Gordon Brown has slipped quickly out of view, but you can't keep Tony Blair out of it. The Iraq Inquiry reminds us of his most fateful decision; he pops up to talk about Egypt as the Middle East peace envoy.

The Blair brand is cited regularly in the political debate about public services. It suits David Cameron very nicely to present the Coalition Government's education, welfare and health reforms as completing Mr Blair's unfinished business. Mr Cameron has read the Blair memoirs closely and has been heavily influenced by the former prime minister's admission that he wasted his first four-year term and wished he had had gone "further and faster" after each public service reform.

This week, Mr Cameron deployed a classic Blair argument, his "modernise or die" mantra. He argued that, with the NHS facing huge financial pressures, the Government could not afford not to press ahead with its plans to transfer 80 per cent of the budget to GPs because this would bring big administrative savings. He even suggested that failing to modernise would put at risk the fundamental principle of an NHS free at the point of use.

Conversely, sceptics worry that the pressure to make unprecedented efficiency gains of 4 per cent a year make this precisely the wrong time for the massive upheaval of abolishing primary care trusts (PCTs), whose commissioning role will be transferred to GPs. The doubters including many Liberal Democrat MPs.

The bad news for Mr Cameron is that a lot of Tory MPs share the doubts. Their appetite for radical reform in schools and the benefits system does not extend to the NHS, and they believe the health reforms could turn into a slow-motion car crash with heavy casualties at the next general election. Despite Mr Cameron's warning that the status quo is not an option for the NHS, they would prefer to let sleeping dogs lie.

Such a reassurance strategy was the name of the game before last year's general election and Mr Cameron did a good job. His moving experience with his late disabled son Ivan underlined his personal commitment to the NHS. A pledge to raise the budget each year in real terms also helped to neutralise the issue.

Why, then, is the Prime Minister apparently taking such a risk now? There are two reasons: Andrew and Lansley. Before the election, the Health Secretary's brief from Mr Cameron was to keep a lid on health and get the professionals onside. He achieved the latter by pledging to scrap Labour's targets and promising no more top-down reorganisations.

True, Mr Lansley did talk about practice-based commissioning, but the full implications were not spelt out. Now the professionals queue to attack yet another top-down reorganisation. Mr Cameron argues, unconvincingly, that it is a "bottom-up" one.

In the Commons this week, Mr Lansley joined the Blair fan club, presenting his changes as evolution not revolution, a continuation of his market-based reforms such as payment-by-results, all hospitals having foundation status and GP commissioning.

Cameron allies suggest he is quite happy to have a row about the reforms (he prefers the word "modernisation" these days) because it shows his Government is not just about cuts, cuts and more cuts. It is a high-risk strategy.

Although the plans do decentralise power, they may not devolve blame when things go wrong. Mr Lansley may deserve credit for handing over the reins to an independent commissioning board. But have public expectations really changed since Aneurin Bevan, the founder of the NHS, said he wanted a bedpan dropped in a hospital corridor to reverberate in Whitehall?

Mr Lansley should ask Patricia Hewitt, Labour's former health secretary. She inherited what was euphemistically called a "reconfiguration" exercise to balance the books, which in practice meant hospital closures. She came through the firestorm, just.

Yet Labour doubled the NHS budget. If the Coalition injects more market forces, there will be a lot more reconfiguring to do at a time when the budget is (at best) at a standstill due to the pressures of medical advances and an ageing population.

Doing more for less will mean more rationing. Who or what will get the blame when a local hospital runs out of money and faces closure? Patient choice? I don't think patients will blame themselves. The GP consortiums? I doubt it. The Government? Almost certainly. The same applies on waiting times, surely bound to rise as targets are abolished. Mr Lansley will surrender the power to intervene, but that will not stop the public clamour for him to do so when services fail.

Tory MPs who have thought through the reforms smell danger. "We are playing with fire," said one senior backbencher. No one would be happier than Labour if the next election becomes a referendum on the NHS. Just as Labour has lost its hard-won trust on the economy, the reforms could easily revive fears that the Tories are not to be trusted on health, which Mr Cameron has worked so hard to allay.

Mr Cameron and Mr Lansley will portray Labour as wanting to pump in extra money while being against modernisation. "Spending bad, reform good" will be their message. Yet there are huge risks in sweeping changes when money is so tight. The right lesson from the Blair era is that you need both money and reform. The great NHS shake-up is a gamble Mr Cameron may live to regret.