Jeremy Corbyn is already facing a backlash within Labour ranks after appointing one of his most hardline left-wing allies as shadow chancellor.

Serial rebel John McDonnell has been handed the crucial task of overseeing the party's economic policy in a team that Mr Corbyn's aides described as "refreshing" and "dynamic".

Former leadership rival Andy Burnham has accepted a job as shadow home secretary, although a host of significant players have refused to take on frontbench roles. There has also been criticism that no women are in the most senior positions.

The scale of the problems Mr Corbyn faces were underlined as Hilary Benn, who is staying on a shadow foreign secretary, declined to offer full endorsement for Mr McDonnell's appointment.

Asked if he was 100% behind the move, Mr Benn told BBC Radio 4's Today programme: "This is the choice that Jeremy has made. I respect the choice that Jeremy has made as leader.

"We have just come off the back of two bad election defeats for the Labour Party, and our principle task is to win the people's trust when it comes to the economy.

"John's first and last task as shadow chancellor will be to win the trust and confidence of the British people in arguing for a different economic policy."

Pressed on whether he welcomes Mr McDonnell taking charge of the Treasury brief, Mr Benn said: "I welcome everybody who is serving in Jeremy Corbyn's cabinet... because Jeremy won a thumping victory, we have a responsibility to rally round him."

He went on: "Jeremy has appointed people to his shadow cabinet who he knows have different views to him on some issues of policy.

"That is about a different kind of politics. One of the reasons I think he won such a large mandate was partly about policy for some people, but also because he represents something different.

"He is going to respect the different views that people have got, and we have got to respect each other. It will be for the shadow cabinet and then ultimately for the Labour Party to decide what our policy will be going forward."

Mr Benn, the first senior member of the new-look front bench to appear on the airwaves, attempted to calm fears among many Labour MPs that Mr Corbyn could campaign for Britain to leave the EU in the in/out referendum expected next year.

Chuka Umunna stood down as shadow business secretary complaining the new leader had refused to give him an assurance he would not back a "Brexit" vote.

But Mr Benn said: "He wants to ensure that Europe in particular works better for working people.

"Jeremy said whatever differences we may have with some aspects of European policy and whatever reforms we want to see, we will stay to fight together for a better Europe."

Mr Benn also dismissed concerns about the lack of women in the top posts - traditionally considered to be shadowing the chancellor, home secretary and foreign secretary.

"It all depends on your definition of top job," he said. "That is a slightly old fashioned view. International development, Diane Abbott is going to be doing that. The refugee crisis has taught us how important it is to play our part in supporting people.

"Education of our children is vital, Lucy Powell is going to be doing that., And Angela Eagle, as well as being shadow business secretary, she is going to be the shadow first secretary of state."

Chris Bryant said he had turned down the defence brief, citing major policy differences with Mr Corbyn, but will still serve in the frontbench team as shadow Commons leader.

"I think Jeremy needs somebody in that particular portfolio where he and that person are rather more at one than I could be," the Rhondda MP told BBC Radio Wales.

"As it happens, I'm a sceptic about Trident but on Nato and on defence I believe that the first thing that a government has to do is protect its people.

"I worry that we have not got enough proper armed forces in this country to be able to defend ourselves."

He added: "It's difficult and I think it is going to be a bit of a bumpy ride because there are issues on which - they are not light issues - I profoundly disagree with him, like on Nato, Russia and things like that."

Asked about Labour's electoral prospects ahead of next year's contests in Wales, Mr Bryant struck a cautious note: "I think it's going to be really tough over these years. Even if Nelson Mandela were leader of the Labour Party now I think we would be facing a tough time."

Labour MP Diana Johnson, a former frontbencher, is among those condemning the "old fashioned male-dominated Labour politics" of the reshuffle.

Alongside Mr Corbyn as leader and Tom Watson as his deputy, Mr McDonnell, Mr Benn, and Mr Burnham in the five top roles, Blairite Lord Falconer has been made shadow justice secretary.

In an apparent effort to head off criticism, Labour officials followed up an announcement that Ms Eagle was taking the business brief with news some hours later that she would also be shadow first secretary of state.

That will mean she takes on Chancellor George Osborne at the weekly PMQs sessions when David Cameron is away. However, as Mr Corbyn has already indicated he hopes to rotate responsibility for PMQs around his ministers the significance is currently unclear.

Heidi Alexander is shadow health secretary, Seema Malhotra will be Mr McDonnell's number two as shadow chief secretary and Rosie Winterton remains chief whip.

In a flurry of activity that went on late into the night, ex-shadow environment secretary Mary Creagh joined Mr Umunna in declaring she would not serve under Mr Corbyn, while Ivan Lewis was removed from the Northern Ireland brief despite offering to stay on temporarily to help deal with the political crisis at Stormont.

Liz Kendall, who came last of the four candidates in the leadership race, Tristram Hunt, Rachel Reeves, Chris Leslie, Emma Reynolds and Jamie Reed have all ruled themselves out.

Mr Corbyn was declared Ed Miliband's successor on Saturday on the back of a surge of support from activists that saw him attract a massive 59.5% of votes - topping the ballot among party members as well as trade unionists and new supporters.

Deputy leader Mr Watson said the size of the mandate meant there was "zero chance" of a successful coup being launched to topple the leader, but conceded Mr Corbyn would have to make compromises in key areas.

Union leaders also warned the new leader would have to temper long-held stances - such as his opposition to Britain's nuclear deterrent as well as on Nato and the EU in the interests of party unity.

Mr Corbyn is expected to make his first appearance on the Commons frontbench of his entire 32-year career as an MP later as he leads the party in opposing the Government's anti-strike laws.

He will also address his first meeting as leader of the Parliamentary Labour Party.

Former shadow cabinet minister Caroline Flint ruled out serving in Mr Corbyn's team.

She said she has "decided I can best support the Labour Party and the leadership from outside the shadow cabinet".

Ms Flint admitted it had been a "hard decision to make", but said she would focus on "helping Labour reach out to those voters who turned away from us, but who share many of our values".

She added: "I hope this work will be helpful to Jeremy, the shadow cabinet and the Labour Party as we rebuild over the next five years.

"I remain loyal to the Labour Party and will do everything I can to help us win the next general election in 2020."

Mr Corbyn, who was putting the finishing touches to his shadow cabinet line-up, spent part of the day having a coffee with aides in Parliament's Portcullis House office complex where he was congratulated by supporters.

In a sign of the task he faces in uniting the party, one former minister predicted that the general public would soon realise the hard-left nature of Mr Corbyn and Mr McDonnell's views.

The source predicted that the party could see a short-term poll boost because of the "novelty" of the anti-establishment leader.

But the ex-minister added: "The public will reach its conclusions pretty soon."

The source also expressed surprise at the decision of some moderate MPs to accept shadow cabinet roles despite their policy differences with the leadership.

"I look forward to their first media interviews," the former frontbencher said.

Downing Street said the leader of the Opposition had been invited to join the privy council, which would open the door to him receiving security briefings. No reply has yet been received.

"An invite has been issued to the leader of the Opposition," the Prime Minister's spokeswoman said.

Here are Jeremy Corbyn's shadow cabinet appointments:

Deputy leader - Tom Watson

The West Bromwich East MP was elected as Labour's number two after the third round of counting, beating Stella Creasy.

Despite conceding policy differences with his new leader on key issues, Mr Watson has said there is "zero chance" of a successful coup against Mr Corbyn and he vowed to back him "100%".

Elected to Parliament in 2001, 48-year-old Mr Watson - an ex-flatmate of union boss Len McCluskey - played a small part in toppling Tony Blair and served as minister for digital engagement under Gordon Brown.

He was given charge of the 2015 election campaign by Ed Miliband but quit as deputy chair at the height of the Falkirk candidate selection row in 2013.

Mr Watson gained wider public prominence when he turned his "attack dog" attentions from political opponents to the Murdoch media empire and helped expose the phone-hacking scandal.

Shadow chancellor - John McDonnell

The veteran left-wing MP has been rewarded for propelling his close ally Mr Corbyn to the leadership by becoming the party's spokesman on the economy.

He will be in charge of implementing Mr Corbyn's radical anti-austerity policies while opposing a Chancellor in George Osborne whose stock has never been higher.

The Hayes and Harlington MP has no ministerial experience but has served on committees including a deregulation committee under the last Labour government and more recently the justice committee.

A serial rebel, Mr McDonnell enjoys very close links to the trade unions and favours renationalising the banks.

He recently declared he would "swim through vomit" to vote against benefit cuts in defiance of the party line, and faced criticism for reportedly telling a union event that he would "like to go back to the 1980s and assassinate Thatcher".

Shadow home secretary - Andy Burnham

Having finished a distant second in the party leadership election, Mr Burnham will now have to set his sights on Theresa May rather than David Cameron.

The Leigh MP has been given one of the top roles in the shadow cabinet, an advance on his previous post as shadow health secretary, and will have to take the Home Secretary to task over issues such as the refugee crisis and surveillance.

The passionate Evertonian held a ministerial role in the Home Office under the last Labour government and earned widespread respect for the leading role he played in having the inquiry into the Hillsborough disaster reopened in 2009.

He has also held a ministerial role in the Department for Health, followed by a year as chief secretary to the Treasury and a stint as culture secretary, but has drawn criticism over the Mid Staffs hospital scandal, which took place during his time as health secretary.

Mr Burnham has been dubbed "flip-flop Andy" in some quarters for apparent changes in his approach.

Once considered a Blairite, the frontbencher has since shifted towards the left, turning against the privatisation in the health service that Labour had presided over.

Shadow foreign secretary - Hilary Benn

A survivor of the pre-Corbyn era, Mr Benn retains his post as shadow foreign secretary which he has held since May.

Unlike some of his new shadow cabinet colleagues, he has years of ministerial experience, having served in the governments of Tony Blair and Gordon Brown.

He was secretary of state for international development and environment, food and rural affairs between October 2003 and May 2010.

Since taking over the foreign affairs brief in May, he has questioned the Government's plan to repeal the Human Rights Act (HRA) and faced off with Mr Osborne in the Commons at a Prime Minister's Questions session when the Prime Minister was away.

Shadow first secretary of state and shadow business secretary - Angela Eagle

Seen as a unifying figure of the soft left, Ms Eagle will now have to take on the mantle of implementing Mr Corbyn's radical anti-austerity policies in the business sector.

The Wallasey MP has some Treasury experience, having served as exchequer secretary under Mr Brown and shadow chief secretary under Mr Miliband.

Since vacating that position in 2011, Ms Eagle has taken on the relatively low profile brief of shadow Commons leader where she has worked opposite the likes of William Hague, Andrew Lansley and Chris Grayling.

She was the MP who David Cameron told to "calm down, dear" during an exchange during Prime Minister's Questions.

The PM later apologised for his remarks after being accused of sexism.

The 54-year-old is a keen chess player, having once represented England and winning numerous country championships with Lancashire.

That keen strategic brain may prove useful in opposing Mr Osborne who is seen as a master tactician who uses his Budgets as political weapons.

Shadow health secretary - Heidi Alexander

The MP for Lewisham East will be a new face in the shadow cabinet, having not held a senior post within the parliamentary party before.

She nominated Mr Burnham in the leadership race and served as a whip under Mr Miliband's leadership, after being elected in 2010.

Her campaigning work to save Lewisham hospital's A&E unit may give an indication of the way she will oppose the Government's health policies.

Ms Alexander's commitment to her constituency was illustrated in 2011, when she cut short her honeymoon after the Commons was recalled to debate the rioting which had affected London and other English cities.

Her own constituency office had been vandalised during the disorder and she told MPs: "I first learnt of these events as I sat in a New York taxi, on my way to start my honeymoon. As I listened to voicemails - one from my alarm company, two from the police, I felt physically sick."

Reacting to her new role on Twitter, she said: "Humbled to serve as Shadow Health Secretary. The NHS is facing immense challenges & I will do all I can to hold this Government to account."

Shadow justice secretary - Lord Falconer

Lord Falconer of Thoroton keeps his post as shadow justice secretary after being appointed by Harriet Harman in May.

A former flatmate and close ally of Mr Blair, his appointment will be seen as an attempt by Mr Corbyn to include people from all wings of the party.

He was a supporter of Mr Burnham's leadership bid and faced accusations of sexism after claiming that "neither Yvette (Cooper) or Liz (Kendall) were able to steer the party through the challenging years ahead".

The former lord chancellor has championed right-to-die legislation, which ran out of time in the House of Lords before being revived by another MP this year.

Shadow chief secretary to the Treasury - Seema Malhotra

The Feltham and Heston MP will work closely with shadow chancellor John McDonnell as part of the new look Labour Treasury team.

She was elected in 2011 before becoming the party's first shadow minister tasked with tackling violence against women and girls, working alongside then shadow home secretary and defeated leadership hopeful Ms Cooper.

Ms Malhotra was a vice-chair of Ms Cooper's ill-fated leadership campaign.

Shadow secretary of state for international development - Diane Abbott

An ally of Mr Corbyn, the left-wing MP for Hackney North and Stoke Newington has been rewarded for her support with a place at the shadow cabinet table.

Ms Abbott was defeated in the London mayoral race by Sadiq Khan last week and was also a beaten leadership candidate against Mr Miliband in 2010, before later serving a brief spell in his shadow cabinet.

She has been an outspoken critic of many of her own party's policies over the nearly three decades since she became the first black woman to be elected to the House of Commons.

She has said her party's leader will not seek Britain's exit from Nato or the European Union but will maintain opposition to the renewal of Trident.

Chief whip - Rosie Winterton

The retention of the well-respected party disciplinarian, who filled the role throughout Mr Miliband's tenure as leader, could be an important element of maintaining unity.

Born in Doncaster, the 57-year-old was head of then deputy Labour leader John Prescott's office before being elected to represent her home town in 1997.

She served in a succession of ministerial roles under both Mr Blair and Mr Brown.

Shadow leader of the House of Commons - Chris Bryant

The former curate has had a colourful political career, including posting a selfie posing in skimpy underpants for a gay dating site.

In 2003, pictures procured from his Gaydar profile were published alongside transcripts of sexually explicit messages he sent to other site users.

A staunch pro-European, Mr Bryant acknowledges he has major policy differences with Mr Corbyn and predicted a "bumpy ride" for the new leadership.

He was a victim of phone-hacking and has campaigned for greater press regulation - a stance which is unlikely to change despite his shift away from the shadow culture portfolio.

Although he had been viewed as an arch-Blairite, Mr Bryant was one of the prime movers behind a 2006 letter calling for the former prime minister to stand down.

Shadow education secretary - Lucy Powell

A key player under Mr Miliband, including acting as his chief of staff, Ms Powell was seen as instrumental in him winning the party leadership.

She was the vice-chair of the 2015 general election campaign, with a role taking responsibility for the party's day-to-day operations.

Ms Powell, who entered parliament at by-election in 2012, nominated Mr Burnham for the leadership warning that the party had a "mountain to climb" to regain the trust of the public.

An Oxford graduate, she said the education brief was a "role I'm passionate about" and one "where I hope to make a difference".