Former health secretary Alan Milburn has branded the coalition's watered down NHS reforms the "biggest car crash" in the service's history.
The Labour ex-MP, currently advising David Cameron on social mobility, said the taxpayer faced writing "a very large cheque" as billions of pounds in efficiency savings would not be achieved.
The condemnation of the revised plans, which were unveiled earlier this week, came in an article for the Daily Telegraph.
"The Government's health reforms are the biggest car crash in NHS history," he wrote. "The temptation to elevate short-term politics above long-term policy proved too much for both David Cameron and Nick Clegg.
"Many in both camps inside the coalition consider the U-turn a triumph. But it has the makings of a policy disaster for the NHS and, maybe in time, a political disaster for the Government. It leaves both health policy and British politics in a very different place."
Mr Milburn said the Prime Minister was likely to be seen as more "protectionist" than either of his Labour predecessors, despite his insistence that the changes were pro-market.
"The promise of the coalition was that it would go where New Labour feared to tread when it came to public service reform. There would be no no-go areas," Mr Milburn wrote.
"In fact David Cameron's retreat has taken his party to a far less reformist and more protectionist position than that adopted by Tony Blair and even that of his predecessor Gordon Brown."
Mr Milburn described the new policy as the "biggest nationalisation since Nye Bevan created the NHS in 1948". Mr Cameron had handed over control to "the daddy of all quangos", the NHS Commissioning Board.
The ex-Cabinet minister said scrapping the 2013 deadline for giving GP consortia control of commissioning would result in a "patchwork of decision-making for years to come".
Turning to the need to make £20 billion of efficiency savings, he asked: "So how will the NHS books be balanced?
"By the usual device which policy-makers have deployed every decade or so in the NHS. A very large cheque.
"It was precisely the situation David Cameron and George Osborne were trying to avoid. Sorry George, but the cash you were saving in your pre-election Budget for tax cuts will now have to be spent on a bail-out for the health service."
A government source said in response to Mr Milburn's comments: "Eight years ago, Alan Milburn tried to reform the NHS but failed to deliver the progress necessary because he was blocked by Gordon Brown.
"Other former Labour health ministers - and many professional bodies - support the reforms as a necessary evolution.
"We can't afford to miss another opportunity to improve the NHS."