Before the general election David Cameron could claim, without fear of ridicule, that the NHS would be "safe in our hands". Now Andrew Lansley, his Health Secretary, is heckled in the street, the medical profession is in revolt and a member of his cabinet has compared the health reforms to the poll tax. Having declined every opportunity to drop the bill, the Prime Minister has resolved to fight on at great political cost. The Conservatives are trailing Labour by 15 points as the party that has "the best approach to the NHS" and just 20 per cent of voters believe the NHS is "safe in David Cameron's hands".

The most recent Downing Street health summit, intended to give the appearance of a "listening" government, achieved the opposite. By excluding groups such as the Royal College of General Practitioners, the Royal College of Nursing and the British Medical Association, all of which have called for the bill to be dropped, the government only underlined the opposition to its reforms.

True, the medical profession has often been resistant to change. It was only after Aneurin Bevan, in his own words, "stuffed their mouths with gold" that BMA members dropped their objections to the creation of the NHS. But it is the range and persistence of the opposition that distinguishes this from previous revolts. As David Owen, a doctor and one of the founders of the Social Democratic Party, has argued, Clement Attlee had a clear mandate after the Labour landslide victory of 1945 to implement bold reforms but Mr Cameron does not. Having promised an end to "top-down reorganisations" of the NHS, the Prime Minister has no grounds for complaint.

In a notable intervention on page 34, the former health secretary Alan Milburn, whom some have been touted as an "impartial" replacement for the hapless Mr Lansley, writes that because of the Health and Social Care Bill, "riddled with complexity and compromise", the Conservatives have "forfeited any claim to be the party of NHS reform". Now that the Tories have been discredited, he urges Labour to embrace "market disciplines, customer focus and value creation". Yet Labour should be wary of the rhetoric of the market in health care. A study by the London School of Economics (Does Competition Improve Public Hospitals' Efficiency?) finds that while competition within the NHS has improved standards, competition with private providers has not. Providers have cherry-picked the easiest cases, leaving the health service to struggle with the rest. As a result, waiting times have risen fastest in NHS hospitals competing with private counterparts.

It is this fate that the bill, with its requirement for GPs to commission services from "any qualified provider", threatens to impose on the entire service. By subjecting the NHS to EU competition law for the first time, the government will give priority to cost over quality. There is still time, however, to prevent what private-sector providers gleefully refer to as the "denationalisation" of the NHS. Anticipating their spring conference, Liberal Democrat activists have submitted an emergency motion calling on the coalition to scrap the competition chapter of the bill. This would remove the most pernicious aspect of the legislation and allay the fears of many medical professionals, on whose confidence the NHS depends. The motion correctly calls on ministers to publish the official "risk register" detailing what could go wrong as a result of the reforms. With the NHS simultaneously required to undergo the biggest reorganisation in its history and make efficiency savings of £20bn, the potential for upset is huge.

As he searches for points of differentiation from the Tories, Nick Clegg has an opportunity to stake his claim to be the last defender of the NHS. It is one that he must take.