Andrew Lansley and Norman Lamb in fight to the death over NHS reforms

Health secretary blocked ministerial post for respected Liberal Democrat MP who has now turned on controversial NHS reforms

Norman Lamb MP has voiced opposition to the pace of Andrew Lansley's health reforms

Norman Lamb has threatened to resign as a government whip unless a series of demands on the NHS reforms are met. Photograph: Martin Argles for the Guardian

Andrew Lansley must be regretting one of his first acts as health secretary last May when he blocked Norman Lamb, his Liberal Democrat counterpart, from becoming a minister in his department. Lansley and Lamb, two of Westminster's greatest experts on the NHS, had had an almighty falling out in the run up to the general election over the financing of long term care for the elderly.

On the eve of the coalition's first anniversary that veto is coming back to haunt Lansley who deprived the department of health of a canny political operator. Lamb has the ear of Lib Dems at all levels of the party and would have made a much better job of finessing the NHS reforms.

Lamb showed that he remains a potent political force on Sunday when he broke months of silence to warn that he will resign as a government whip unless major changes are made to the government's NHS reforms. Lansley plans to abolish Primary Care Trusts and hand 60% of the NHS budget to new GP-led consortia.

The Lamb message was clear. Unless his warnings are heeded Lib Dem MPs and peers will struggle to support the health and social care bill when it is revived in June after a two month "listening exercise". Nick Clegg would also face an embarrassing resignation from his frontbench team.

The warning from Lamb sets the stage for something of a showdown in which there will probably be a loser and, possibly, no winner. If Lamb is not happy he will resign because friends say he accepts his position will be "terminal" if his warnings are not heeded.

But if Lamb wins Lansley will be a lame, if not a dead, duck. Lamb's principle demand – that GPs should be free to opt into Lansley's new GP-led consortia – would be a step too far for the health secretary. Lansley would fear that the Lamb proposal would create a two-tier NHS. He would probably not want to hang round in those circumstances.

It is worth taking a look at the background to the Lansley / Lamb feud before working out the consequences of today's events. The two men fell out during the all-party negotiations, launched by the Labour health secretary Andy Burnham before the election, over the funding of long term care for the elderly. Lamb and Burnham thought the Tories acted in a rather sharp manner when they started running a campaign against a so called "death tax".

Wind forward to the formation of the coalition government when the new health secretary wielded his veto. Lamb was advised that he would instead be appointed as a minister of state in the department for international development. But when Lamb telephoned officials at the department he was told DfID was expecting the Tory MP Alan Duncan.

Clegg then cobbled together a job for Lamb who was made a junior whip. Lamb was given an enhanced role when he was also appointed Chief Parliamentary and Political Adviser to the deputy prime minister.

Lamb was deeply upset at the way he was treated. But he has impressed colleagues with the dignified way in which he rebuilt his career.

The Lansley veto led to the appointment of Paul Burstow, the Lib Dem chief whip in the last parliament, as a health minister. Burstow has a strong track record on health (he was the party's main spokesman between 2003-05) but, as I blogged last week, he shares Lansley's main weakness: poor political antennae.

Lamb has known for months that the Lansley reforms – to hand 60% of the NHS budget to GP-led consortia – would create trouble. As a senior adviser to Clegg and a government whip, he has said nothing publicly – until this weekend. He now believes that the "pause" in the health and social care bill, while ministers embark on a two month long "listening exercise", provides an opportunity for him to voice his concerns.

One source said:

Norman has been extremely concerned about these reform proposals for a long time and has been in a very very difficult position. He decided that the period for reflection was the moment to come out and say it. Sometimes you just have to say what you think.
There are a load of people who are reformers by instinct across the political spectrum, from Alan Milburn to Norman and many Tories. Lansley has managed to unite the reformers and the Luddites in opposition to what he is doing.

Lansley will be irritated by Lamb's intervention, not least because his former sparring partner was involved in advising the Lib Dem negotiators during the coalition negotiations. I blogged last week that the coalition agreement proved a mixed blessing for Lansley. It ruled out "top-down reorganisations of the NHS" but indicated that GPs would have commissioning powers and also indicated that Primary Care Trusts would survive.

But Lamb also has a difficult record to defend. He told the Politics Show on Sunday that "clusters of Primary Care Trusts" would have to be maintained to keep an eye on the "performance management" of GPs. But the Liberal Democrat general election manifesto suggested that PCTs should be abolished:

We will change this by...empowering local communities to improve health services through elected Local Health Boards, which will take over the role of Primary Care Trust boards in commissioning care for local people, working in co-operation with local councils.

Lansley has seized on this paragraph – and the pledge in the Tory manifesto to hand commissioning powers to GPs – to hail his reforms as a marriage of the two parties' proposals. One Lib Dem said it was wrong to interpret the Lib Dem manifesto in this way:

What Lansley says is not true and he knows that. Our manifesto argued for democratic representation on the Primary Care Trusts. What our manifesto meant was in effect electing the board rather than appointing it and naming them Local Health Boards.
Nobody has the faintest idea what a Primary Care Trust does out there in the real world. If you have something called a health board it might have a bit of a hint in its name. The coalition agreement on our commitment to have elected people on the board.

Lamb has put down a highly significant marker. If Lamb wins Tories will complain that too many concessions are being granted to the Lib Dems. But if Lansley wins the Lib Dems will say the Tories are riding roughshod over their party. They may also ask why their leader was so careless about a respected member of his frontbench team when the coalition was formed.