Ministers fear that the National Health Service could require an emergency cash bailout before the next general election to enable it to cope with the escalating demands of an ageing population.
The Chancellor, George Osborne, has promised a real-terms increase in health spending over the next four years. But there is growing anxiety within the Government that the extra money will not be enough to provide care for the growing number of elderly patients and meet the rising cost of advanced medical treatments.
Mr Osborne and the Health Secretary, Andrew Lansley, are calling for £20bn of efficiency savings in the health service over the same period, without cuts being made to services provided to patients.
One minister conceded yesterday that the combination of factors was likely to mean the NHS would need more money before the election, which is expected in 2015. "That would mean having to reopen the spending settlement, which would be a huge problem for us. But it is hard to see how it can be avoided," he said.
The warning emerged as the Government's controversial NHS reforms dominated the Commons yesterday, with Ed Miliband likening them to the poll tax and Labour staging a full debate on the issue.
Meanwhile, the medic who was reprimanded by his health authority for condemning the reforms in a letter to The Independent was named yesterday as Professor John Ashton, NHS Cumbria's director of public health.
He was summoned to a meeting with the trust's chief executive, Sue Page, to explain himself. Labour raised the issue in the Commons on Tuesday claiming it was evidence of NHS managers trying to bully critics into silence.
An NHS Cumbria spokesman said clinicians were always free to express their opinions as individuals but had to be clear they were not speaking on behalf of their employers.
"NHS organisations must always remain non-political. The meeting with Professor Ashton this week is not a disciplinary meeting but is to ensure that he is always mindful of these differences," the spokesman said.
However, in an essay published yesterday in The Lancet, Professor Ashton stepped up his attack on the Health and Social Care Bill. He argued it marked the beginning of a return to an insurance-based system that would recreate the division between the wealthy, who could afford care, and the "undeserving poor".
With the Bill set to return to the Lords next week, there is growing dismay on both sides of the Coalition over the impact of the planned reforms on Tory and Liberal Democrat fortunes at the next election.
"Every time there's some kind of mistake or a hospital unit closes it will get blamed on the reforms," a minister said.
But there is widespread agreement within the Coalition that the plans are far too advanced – and too much political capital has been spent on them – for the Bill to be ditched.
In yesterday's exchanges, Mr Miliband claimed that the Prime Minister had lost the confidence of health service staff. Mr Cameron retorted that the reforms would save the NHS and accused the Labour leader of opportunism.