After his speech to the NHS Alliance conference in Manchester last week, Mr Lansley told GP newspaper that in order to put commissioning responsibility in the hands of GPs: ‘We would need a new contract. And legislation, too.'

A Conservative spokesman confirmed the UK-wide contract would be split up, as the commissioning policy would be enforced in England only.

Mr Lansley insisted that the ‘real budgets' GPs will be handed to buy and organise health services locally will be kept separate from practice income: ‘If [GPs] have a deficit on their budget it doesn't come out of their practice's income.'

However, GPs who persistently fail to balance the books could lose their contracts, the Conservative spokesman made clear.

Mr Lansley also confirmed that GPs will be able to let GP consortia or private firms commission on their behalf.

Following ‘considerable discussions' with the GPC, the Conservatives are now working on the best way to use data to work out how much GPs are allocated.

The shadow health secretary added that the outcomes-focused QOF the Conservatives plan to develop should mean GPs' efforts to redesign services are rewarded as public health improves.

GPC chairman Dr Laurence Buckman said he would discuss funding plans for GP commissioning in detail only if the Conservatives are elected next year.

But his main concern was how GP income is kept separate from commissioning performance. He suggested GPs may be put off if their basic income was under threat.

He added: ‘What happens if the money runs out? What happens to GPs who are not trained or not very good, at managing budgets?'

Dr Buckman was also concerned about GPs being able to hand commissioning responsibility to private companies. ‘Consortia aren't a worry, private companies are. That will allow the private sector to get into all sorts of things, like commissioning services from themselves.'

• Read this week's GP dated 30 October for the full version of this story