Former Labour health secretary Alan Milburn has rejected a government offer to become a candidate for the chair of the NHS Commissioning Board.

Mr Milburn, heath secretary from 1999-2003, was asked by the incumbent, Andrew Lansley, to join the competition for the post. Both the offer and Mr Milburn’s refusal came within the last few weeks.

The post has been advertised since February with pay of up to £63,000 for two to three days a week, split between Leeds - where the board will be based - and London. An appointment is expected in the spring.

NHS chief executive Sir David Nicholson has already been announced as the board’s chief executive.

Last year Mr Milburn agreed to be an adviser to the coalition on social mobility, signalling his willingness to work across political boundaries. However, senior sources close to the reform process suggested Mr Milburn may have rejected this offer because the likely political row over his appointment posed too great a risk given the uncertain outcome of the selection process.

Mr Milburn expressed concern about the reforms at last week’s Nuffield Trust summit. He said some elements of the coalition’s plans were “instantly recognisable” as a continuation of the reforms he oversaw. But he claimed to be “mystified” by the “presentation” of the government’s programme and the lack of “advocacy and advocates” for the changes. “I don’t understand the politics”, he said.

Nick Seddon, deputy director of think tank Reform, said Mr Milburn could have helped win support for the government’s proposals and this may well have outweighed any Tory concerns about his politics.

He said: “Alan Milburn is an extremely powerful figure and one thing he is really good at is politics and communications.

“He understands healthcare and is certainly a serious reformer. He could have helped stop the changes becoming a party political football.”

Mr Milburn declined to comment on the story.