A growing number of England's 36,000 family doctors believes the NHS is "finished", ministers will be warned by leaders of the British Medical Association.

Dr John Chisholm, the BMA's chief negotiator for GPs, will deliver the warning at the start of negotiations which will pave the way for a revolution in the way that family doctors deliver their care. Dr Chisholm has told colleagues that "a growing minority" of family doctors in the BMA believes the NHS will never be able to cope with the rising demands as a tax-based service, free at the point of delivery.

More doctors are calling on the BMA to support a small charge of around £5 to £10 for patients who visit the GP to weed out unnecessary calls.

The BMA said it is prepared to accept change for higher fees for family doctors. Last week it launched its first comprehensive survey of GPs' opinions in a decade which should be complete in October. It has already balloted GPs on whether they would be prepared to leave the NHS and offer patients private care, if the negotiations fail. They overwhelmingly voted yes.

Ministers regard the rumblings from GPs as the opening shots in a tough negotiation about the way family doctors are paid. Alan Milburn, the Health Secretary, has given the NHS Confederation negotiating powers for the Government to reach a deal over the reform of the GPs' contract by early next year.

Under the current contract, 60 per cent of the GPs' income is paid for the number of patients on their list. It was raised from 40 per cent by Kenneth Clarke, then Tory health secretary, to stimulate competition for patients but both doctors and ministers believe it rewards the status quo.

"All it does is pay doctors for long lists of patients, and sometimes poor service," said a senior BMA source. The BMA will go into the negotiations prepared to accept a cut in the "capitation" fees in return for higher pay for other services, including longer surgery opening hours, night calls and special clinics to meet the Government's targets for improving the nation's health. The Government's 10-year NHS plan envisages radical changes to the "Dr Finlay" system set up 50 years ago. Ministers want more control over the service provided by GPs; they want more to opt out of the national contract and more GPs to be paid NHS salaries for delivering care in areas of unemployment, ethnic communities, and the inner cities, or take on contracts for personal medical services.

The most controversial issue which could provide a stumbling block to a deal is the Government's manifesto commitment that by 2004 all patients will be able to see a doctor within 48 hours.This is seen by the BMA as a possible threat to the traditional doctor-patient relationship.