Boris Johnson will be a member of David Cameron's political cabinet but not a minister, the Prime Minister confirmed, as he appointed the rest of his government.

The newly-elected MP for Uxbridge and South Ruislip walked in through the famous black door carrying his cycle helmet and Mr Cameron swiftly revealed the appointment on Twitter.

Other Cabinet appointees announced on the first working day of the new Conservative-only Government included Sajid Javid as Business Secretary, in a promotion from culture, media and sport, replacing Vince Cable in one of a number of posts left empty by the end of the coalition with the Liberal Democrats.

Former Commons Culture Committee chairman John Whittingdale replaces Javid as Culture Secretary, with next year's 10-yearly renegotiation of the BBC's Royal Charter at the top of his in-tray. Mr Whittingdale last year described the BBC licence fee as "worse than a poll tax" and said it was "unsustainable" in the long run and needed tweaking immediately.

Hastings and Rye MP Amber Rudd is one of a number of women being promoted by Mr Cameron, moving upwards within the Department for Energy and Climate Change from a junior ministerial position to the Cabinet-level Secretary of State role vacated by Lib Dem Ed Davey, who lost his seat last week.

Mr Johnson had not been expected to take a big spending department while serving out his final term as London mayor, and Mr Cameron said that he would "devote his attention" to his mayoral duties over his remaining year at City Hall.

The political cabinet includes all the key figures at the top of the Government but excludes civil servants as matters discussed are party political. No minutes are taken at the meetings, expected to take place fortnightly at 10 Downing Street following the weekly meeting of the full Cabinet, which formally agrees policy and sits at the heart of government.

Mr Johnson's spokesman said: "The mayor has accepted an invitation from the Prime Minister to attend political cabinet.

"This is not a ministerial appointment. He won't be attending full Cabinet and won't be running any department.

"The mayor has always been clear, he has to fulfil his mandate running London first, and that's exactly what he will be doing until his term ends in May 2016."

Priti Patel will replace Esther McVey, who lost her seat, as Employment Minister. She will attend Cabinet but will hold the rank of minister of state.

And the Prime Minister confirmed Baroness Stowell would be promoted to full Cabinet rank as Leader of the Lords.

Iain Duncan Smith is to remain in charge of the Government's controversial welfare reforms as Work and Pensions Secretary, Mr Cameron has also announced.

The former party leader is one of a number of senior figures keeping their jobs, including Chancellor George Osborne, Home Secretary Theresa May, Foreign Secretary Philip Hammond, Education Secretary Nicky Morgan and Defence Secretary Michael Fallon.

It has already been announced that Michael Gove is returning to the top of government - moving from chief whip to Lord Chancellor and Justice Secretary at the expense of Chris Grayling, who becomes Leader of the House of Commons.

Mark Harper, who quit as immigration minister over the work status of his cleaner, takes over from Mr Gove as chief whip.

Robert Halfon, who was the Chancellor's parliamentary private secretary (PPS) in the last parliament, has been appointed deputy chairman of the Conservative Party.

Terry Scuoler, chief executive of manufacturers' organisation EEF, said of the new Business Secretary: "Mr Javid will need to focus on three things in particular: building on the success of the previous administration's work on industrial strategy and ensuring this is applied across Government; maintaining funding for important levers of growth, including research and innovation; and support for exporters, through UKTI (UK Trade & Investment) and helping ensure Government delivers the big-ticket infrastructure projects, from the new airport hub to rail and road improvements."

John Cridland, CBI director general, said: "We congratulate Sajid on his appointment as Business Secretary. He was an excellent Treasury minister and will be a strong voice for the business community, helping to make its voice heard loud and clear at the cabinet table."

John Longworth, director general of the British Chambers of Commerce, said: "From the business perspective, the two biggest priorities in Sajid Javid's in-tray should be kick-starting a revolution in exports, to get more companies trading around the world, and working with us to ensure that firms can get new recruits with the skills and motivation to get ahead in the world of work."

Mr Cameron later confirmed that Patrick McLoughlin is to carry on as Transport Secretary in the new Cabinet.

Liz Truss, who had been tipped for promotion in the reshuffle, will also continue Environment Secretary.

Anna Soubry has been moved sideways from minister of state for defence to minister of state in the Department for Business, Innovation and Skills, where she will have responsibility for small business. She will attend Cabinet.