The list included a former chairman of the British Medical Association, former presidents and vice-presidents of several royal colleges, medical school deans and numerous emeritus professors and leaders in research. Their specialties stretched to all corners of the profession, from epidemiology, public health, paediatrics and orthopaedics to surgery, sexual infections, renal medicine and general practice.

Eight years on, and many of the same doctors talk not of a health service rescued, but of a Government that has pursued policies as damaging to the fundamental tenets of the health service as the Tory initiatives they so feared.

Many said that, although the number of doctors and nurses may have increased, the power now wielded by managers, who have doubled in number to more than 37,000 since 1997, was turning the NHS into a service that values accountancy over patient care.

Increased use of the private sector for healthcare and building hospitals has also raised the hackles of the medical establishment, and the introduction of competition between institutions is viewed as one of Labour’s biggest betrayals.

The alarm among signatories of the 1997 letter was already evident in 2003, when Vincent Marks, the former dean of medicine at the University of Surrey, was moved to seek the views of his colleagues about plans for foundation hospitals and treatment centres.

Of the 35 who replied to his concerns about the divisive impact of the policies, all but two said they shared his disapproval.

Nigel Speight, a consultant paediatrician based in Durham, told The Times that he and several colleagues had considered writing to the Prime Minister about the creeping privatisation of the NHS.

After 24 years as a Labour Party member, Dr Speight resigned two years ago because of the Iraq war and the Government’s “broken promises” on health.

“I never dreamt that a supposedly Labour Government could do so much damage to the fabric and principles of the NHS, which they initially created,” he said.

Chaand Nagpaul, a GP from Stanmore in northwest London, said that, although some improvements were evident, the means by which Labour had achieved them had undermined the profession’s trust in the party as guardian of the health service.

He added: “Labour has undoubtedly made some progress, but there are policies that will fragment the NHS exactly the same way that the Tories did. Many doctors now feel disappointed and surprised. The administration has let down the goodwill of a great number of us.”

Although some doctors said that the extra government funding had achieved little, a minority praised a rise in standards and found little to criticise in Labour’s approach.

Aneez Esmail, Professor of General Practice at the University of Manchester, said that the NHS had undergone a big transformation and that critics should not forget its parlous state in 1997.

“We have gone from being understaffed and underfunded to seeing a great deal of investment and having more doctors and nurses,” Professor Esmail said. “I think many of those who are critical have very short memories about what the situation was like under the previous Government.”

A survey of medical professionals, published in Hospital Doctor this month, offered further evidence of shifting opinions on Labour. Of the 700 doctors asked for their voting intentions, just 13 per cent said they planned to vote Labour, compared with 28 per cent at the time of the last election in 2001.

In comparison, 27 per cent of hospital doctors said that they would vote Conservative, up from 20 per cent in 2001. The poll indicated that 21 per cent planned to vote Liberal Democrat, compared with 15 per cent in 2001.

John Reid, the Health Secretary, told The Times this month that there was no indication that support was waning: “Our lead and the support we have for reforms of the NHS is far greater than two years ago. That’s a fact.

“All the indications are that support for the NHS [under the current Government] is strengthening.”

Mr Reid said that one point of contention for some doctors was the Government’s drive to give patients greater control over their healthcare.

He said that, although such changes might pose challenges, they were as nothing compared with the risks of leaving the health service in its former state. “We are putting patients at the centre of the system,” he said. “That throws up challenges for staff, there is no doubt about it. I fully understand that as we get more assurance and quality and power to patients there will be some [doctors] who perceive that they are getting the challenges and instabilities that patients once had.

“Whatever this minority think that’s difficult about risk of change, let me assure them there would be a far greater one if the NHS had not changed.”

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