David Cameron was rattled in the Commons today by an attack on his health reforms - and with good reason. The NHS reorganisation is a disaster on many fronts. It is unloved by doctors, poorly understood by the public and, after a series of mangling amendments in parliament, barely even resembles the vision first outlined by Health Secretary Andrew Lansley. The likeliest outcome from the whole thing is protracted chaos and worse services. This time it will be very hard for the Tories to blame the mess on Labour's legacy.

Opinion polls traditionally show Labour well ahead of Conservatives in terms of who is trusted to look after the NHS. Crucially for Ed Miliband, this is also an issue that is personally associated with David Cameron. The pledge to avoid "top down reorganisations" came from Conservative leader's lips. So did the promise to protect health spending in real terms. That will be very hard to achieve even if inflation comes down - at least not without imposing harsher cuts elsewhere. The Labour front bench think the NHS is one policy area where they might be able to puncture Cameron's famous Teflon coating. I have even heard it said by MPs, and not just from Labour ones, that the NHS alone could cost the Tories a majority at the next election

Crucially, Tory MPs are starting to get worried. They are as baffled as anyone else as to how the government got itself into this mess. Questions are increasingly being asked about Lansley's future. It is recognised that he would have to resign if the reforms were shelved. That is hard to do in practice because some of the structural changes are already under way. But as an exercise in political damage limitation it might still be worth slamming on the brakes and, if need be, losing Lansley. Very senior Tories recognise now that the NHS is their point of greatest vulnerability. So much so, in fact, that one source familiar with the Prime Minister's feelings about the subject recently told me Downing Street wished the Lib Dems had killed the thing off last year instead of insisting on a legislative "pause".

Back then Nick Clegg didn't want to be seen to be too obstructive. The Lib Dem priority was still being seen to make coalition work. With hindsight, Clegg's team now say they should have been bolshier and insisted that the NHS reforms be dropped. It is testimony to how politically toxic the whole thing has come that an increasing number of Tories on front and back benches agree.