David Cameron and other senior ministers have been criticised for backing away from public sector reforms amid heavy political pressure.

A thinktank has warned that the Prime Minister's support for key changes to the NHS and other services has "drifted". As a result ministers - such as Health Secretary Andrew Lansley - had been "exposed to attack".

The report from right-leaning Reform came with the Government still struggling to get its controversial health service shake-up through parliament. Ministers have already accepted scores of amendments - and could be forced to make further concessions.

The thinktank examined the state of the coalition's policies to assess the progress being made by departments. While last year saw "undoubted successes" for the coalition's agenda, there were also "reverses and retreats on an equally large scale", it said.

The report praised Justice Secretary Ken Clarke, saying his reform of prisons had presented "the best arguments for competition of any department". Home Secretary Theresa May was said to be saving money at police forces and improving public satisfaction at the same time.

Former defence secretary Liam Fox also rated highly for pushing through radical civil service changes and giving the private sector joint responsibility for managing the defence estate.

However, there was a "contradiction" in education policy giving academies more freedom, while keeping regulation for state schools.

And Mr Cameron's support for public service reform had weakened since he launched the White Paper last year, according to the thinktank.

He had gone from criticising the "old-fashioned, top-down, take-what-you're-given" approach to public services, to "micromanaging NHS waiting times, nursing standards, adoption and troubled families".

"The Prime Minister's commitment to public service reform has wavered and this leaves his reforming ministers exposed to attack."