Deputy PM tells Andrew Marr show that GPs should not be forced to sign up to new commissioning consortiums

David Cameron and Nick Clegg have agreed changes to the government's NHS reforms, allowing the deputy prime minister to launch a ferocious attack on Sunday on the original plans as a "disruptive revolution".

As the Royal College of GPs calls for a radical overhaul of plans to hand 60% of the NHS budget to new GP-led consortiums, Tory sources indicated that the Cameron-Clegg negotiations have left Andrew Lansley an isolated figure in the government's "listening exercise".

Lansley, the embattled health secretary, who is still resisting some of their demands, has been left briefing colleagues that Clegg has embarked on a U-turn after declaring in January that "funnily enough" the NHS reforms were in the Liberal Democrats' general election manifesto.

Clegg gave a taste of the areas of agreement with Cameron on Sunday when he told The Andrew Marr Show that GPs should not be forced to sign up to the new commissioning consortiums and that a 2013 deadline for the changes should be relaxed. The deputy prime minister said: "A lot of people have said to me – and I basically think they're right – they're saying you're going too fast, you're trying to meet artificial deadlines, you're forcing GPs to take on commissioning roles when they might not want to or aren't able to. I basically think they're right.

"I think what we should now do is – which is a change – is an evolutionary approach that only happens […] where people are willing and able to take on these new changes. If not, we shouldn't be forcing the pace according to artificial deadlines in a calendar."

In a sign of his confidence that real changes will be introduced, Clegg said the health and social care bill, which he praised on the same programme in January as an example of the fusion of Tory-Lib Dem thinking, was deeply flawed. "As far as government legislation is concerned, no bill is better than a bad one, and I want to get this right," he said. "Getting these changes right, protecting the NHS rather than undermining it, is now my number one priority.

"I'm not going to ask Liberal Democrat MPs and Liberal Democrat peers to proceed with legislation on something as precious and cherished, particularly for Liberal Democrats, as the NHS unless I personally am satisfied that what these changes do is an evolutionary change in the NHS, not a disruptive revolution."

The Liberal Democrats hailed the deputy prime minister's tough language as a sign of a new assertive relationship with the Tories after the drubbing in the elections last week. Clegg himself heralded this new approach when he said the Lib Dems would act as a "moderating influence" on the Tories. He added: "Where we are dealing with new things – the NHS is a prominent example – we need to bring our particular influence to bear in a very clear manner."

Lord Oakeshott , a close ally of the business secretary, Vince Cable, went even further. He said: "Andrew Lansley is like a mad professor sitting in a secret laboratory mixing up his own magic potion. It has not been through Nice [the National Institute for Health and Clinical Excellence].

"We will have to give it a test to see if it is fit to be let loose on the patient."

But senior Tories, who were irritated with the tone of Clegg's language, said that most of the policy changes highlighted by the Lib Dem leader had been agreed with Cameron.

In a sign that Cameron and Clegg, rather than Lansley, are driving the negotiations, one source said the health secretary has given ground in opening up the GP-led consortiums, though he is still holding out on the role for consultants.

"Andrew Lansley is there on all areas apart from two points," the source said. "So we have to work out what substantive areas he will be agreeing."

Lansley is indicating to colleagues that he may still be prepared for a fight. He is pointing out that Clegg fully endorsed the health and social care bill in an appearance on the Andrew Marr Show on 23 January shortly before every Lib Dem MP present at Westminster, except John Pugh, endorsed the bill at its second reading in the Commons.

Asked by Marr whether the reforms were in the manifesto, Clegg said: "Actually funnily enough it was. Indeed it was...We certainly said we were going to get rid of Primary Care Trusts. We said we were going to get rid of strategic health authorities."The prospect of a showdown between Lansley and Downing Street came as GP leaders warned that the reforms would wreck the NHS.

In a strongly-worded submission, the Royal College of GPs highlights key "risks" inherent in the bill, which seeks to force healthcare providers to compete. It warns that:

• Intensifying competition in the NHS will lead to the service breaking up, drive up costs, damage patient are and less integration of services.

• Family doctors and hospitals could start charging patients for certain services as the bill hands the health secretary's longstanding power to impose fees to the planned new groupings or consortiums of GPs.

• The NHS's mission since its creation in 1948 to provide healthcare to everyone, irrespective of need or ability to pay, could disappear as the Bill removes the health secretary's historic duty of ensuring the provision of a comprehensive national health service.

• The NHS should be "the preferred provider" of NHS services and deeply controversial plans to let "any willing provider" treat patients – including private firms – should be dropped.