The plans fuel fears that the future of GMS is in doubt, following warnings that Scotland could quit the UK deal over widening NHS policy gaps.
GPs will face increasing pressure to abandon GMS in favour of APMS deals that link practices up into large-scale federations, policy experts believe.
NHS Future Forum chairman Professor Steve Field and King's Fund experts said an alternative deal that encouraged practices to federate would allow the DH to press ahead with integrating NHS services while sidestepping 'tortuous' contract negotiations with the GPC.
But the GPC warned that contracts that incentivise integration would move the NHS towards a US system with large commercial companies taking control of general practice.
The NHS Future Forum last week said federations of practices covering 40,000 to 70,000 people could make 'valuable efficiency gains' and deliver a wider range of services.
It said the GP contract should be used to incentivise practices to work more collaboratively - a proposal later backed by the DH (GP, 11 January).
Talking at a King's Fund event on integration, Professor Field said instead of changing the GMS contract, a new APMS-style deal should be introduced to allow practices to integrate on a voluntary basis.
'It's pointless spending years negotiating on the GMS contract. Create an environment where people who want to move forward can,' he said.
GPs could eventually be forced to join. Nick Goodwin, senior fellow at the King's Fund and author of the think tank's major report on the future of general practice last year, said: 'I quite like the idea of it being on a voluntary basis, so you are not actually undermining those individuals that want to practice in a normal way.
But he added: 'Assuming more and more people take on the alternative contract, you begin to isolate those who choose not to so in the end they have no choice.'
King's Fund chief executive Professor Chris Ham agreed that an alternative contract should be introduced to encourage integration.
He said: 'You don't rip up the existing GP contract. Down that route there would be lots of tortuous difficulties and probably unsuccessful negotiations with the BMA.'
Mr Goodwin said over time GPs would opt out of GMS because APMS deals would be 'more lucrative and interesting'. Practices may be eager to federate as they would be better protected against funding squeezes, he added.
'We have already seen that happen in the US, where a squeeze on funding saw practices club together.'
NHS Alliance chairman Dr Michael Dixon agreed there was an appetite among GPs to federate. 'If GPs are remunerated sufficiently to provide properly integrated services I think they would be up for it.'
But GPC deputy chairman Dr Richard Vautrey warned: 'This would effectively take us down the route of health management organisations in the US with individual practices disempowered. We don't need a contract to do this. GPs and practices already work together where appropriate.'