The under-fire £50 billion HS2 high-speed rail project is to get a new chairman in the new year - at an annual salary of £591,000.

The new boss of HS2 Ltd is Network Rail's current chief executive Sir David Higgins who was also former chief executive of the UK's Olympic Delivery Authority.

Australian Sir David is taking over as HS2 Ltd chairman from Doug Oakervee who announced today that he will be standing down at the end of the year.

Sir David, who had already announced he would be leaving Network Rail (NR), will join HS2 Ltd on a one-day-a-week basis on January 1 2014, when he will be entitled to receive pay of £950 a day.

He will take up the post full-time from March 2014 when he will be on an annual salary of £591,000 - which is his exact pay at NR now.

However, it is understood that Sir David will only work full time for six months before taking a three-days-a-week role.

He takes over at HS2 Ltd, the body tasked with developing the HS2 project, at a time when the scheme's value, and need, has been questioned by Labour and others.

Sir David was widely praised for his role in the London Olympics and commentators feel that he has done a good job at NR.

Transport Secretary Patrick McLoughlin said today: "The fantastic work that Doug Oakervee has delivered as chairman of HS2 Ltd is testament to the experience and expertise that he brought to this role.

"His energy and professionalism have ensured that the detailed proposals for phase 1 (from London to Birmingham) of the country's first high-speed line north of London will be introduced to Parliament on schedule later this year."

Mr McLoughlin went on: "The appointment of Sir David Higgins to replace Doug Oakervee ensures that we will continue to have leaders at the heart of HS2 who have a track record of delivery.

"His experience at both NR and as chief executive of the Olympic Delivery Authority - where he oversaw construction of the magnificent Olympic Park, a legacy which will be enjoyed by generations - will be essential to ensure we deliver HS2 on time and on budget."

Sir David, who is in his late 50s, will work alongside HS2 Ltd chief executive Alison Munro.

Earlier today Ms Munro and Chief Secretary to the Treasury Danny Alexander defended the HS2 project in the face of recent criticism and questioning of the scheme's necessity.

In the last few days, Labour has appeared to be cooling towards the scheme, with shadow chancellor Ed Balls questioning whether it might be better for the money to be spent on other schemes.

He told his party's annual conference he would not "write a blank cheque" for the scheme, whose first phase, due for completion in 2026, will see a high-speed line passing through Tory heartlands from London to Birmingham.

Ms Munro said today: "We have never asked for a blank cheque, neither do we want or need one.

"We fully understand the need to keep costs around the project under control. We look forward to bringing HS2 home, on time and within budget."

Mr Alexander said HS2 and the coalition Government's other transport projects are "absolutely essential to the long-term future of our economy".

In a dig at those going lukewarm on the scheme, he added: "It would be absolute folly to neglect these long-term benefits for short-term political reasons."

He said HS2, which has a current budget of £42.6 billion with a further £7 billion earmarked for the trains, could be delivered on time and possibly below budget.

But, speaking at a transport conference in London, he also appeared to indicate there was a possibility there might not be enough time to get the HS2 Hybrid Bill through Parliament before the 2015 general election.

Mr Oakervee said: "I believe HS2 is vital to the growth of the UK economy and will deliver the capacity our rail network sorely needs.

"Sir David is the right man to continue the delivery of this project. I am delighted at his appointment and am confident that alongside Alison Munro, our chief executive, he will continue to drive the scheme forward.

"I am proud of all that I have achieved, particularly that we will be bringing the Hybrid Bill to Parliament by the end of the year, after which I will be standing down. I am pleased to have been able to play a key role in delivering this project which will serve the country for many generations to come."

Sir David said: "I am delighted to be taking up this role. Working at Network Rail I know the challenges we have ahead with capacity on the railways - they are real and we need to take action now.

"I also know the significant benefits that improved journey times between our northern cities will bring not just to the north, but the UK economy as a whole."

He went on: "HS2 is the right solution. It is vital for both passengers and the economy and will put the UK in a different league in terms of infrastructure. My first priority will be to rigorously scrutinise costs to ensure they remain under control.

"HS2 presents a strategic opportunity for this country and I am determined to make sure we take it by delivering a railway that will allow business and communities to prosper in the long term."

Ms Munro said said Mr Oakervee had been "an inspirational chairman" and she described Sir David as "a proven leader with drive, passion and experience".