Members of the British Medical Association passed a motion at their annual conference attacking the present "target payment" system.

In this GPs receive money if a certain proportion of children at their practice are immunised.

Currently, GPs receive up to £910 each year if 70% of infants on their list are immunised, or up to £2,730 if 90% complete their vaccination course.

MMR is one of four childhood vaccinations that have to be given. The uptake of each of these vaccines is added together to determine wheter GPs have met the targets and will get paid.

However, GPs have complained that recent health scares over MMR mean many parents are refusing to have their children vaccinated, which has meant they have lost out on money through no fault of their own.

Right to choose

Dr Richard Vautrey, of the BMA's occupational health committee told the conference he was in favour of MMR, and that his son had recently received his second vaccination.

But he said yesterday, he had seen a mother who did have concerns.

"She is a sensible mum, who wants nothing but the best for her own child, but she still needs a little more time to think about whether she should bring her daughter for the MMR.

"She should be allowed that time.

"She shouldn't be pressured or bullied as as result of some dictat from a Whitehall civil servant, but helped and supported to make the right decision.

"The target system which we find ourselves trying to cope with completely fails in situations like this. Surely parents have the right to say no."

In a snapshot survey of GPs at the conference for BBC Radio 5 Live, a third said their income had been affected by low MMR uptake in the last year.

Almost three out of four of the 51 questioned said that if MMR was removed from the system, it would help them to persuade parents to have their children immunised.

They said the current arrangement is damaging trust between doctors and parents.

A third of the doctors said they had seen an increase in measles cases, and a quarter had seen an increase in the numbers of cases of mumps.

More than half said they had seen the uptake of MMR at their practice go down in the last year, while one third said it had stayed level.

More measles cases

Doctors are suggesting parents should be able to opt out of immunisations in a system of "informed dissent", so if they refuse to have a vaccination they can be taken off the practice's target list for jabs.

The Public Health Laboratory Service said MMR uptake was 83.8% nationally, whereas it should be at least 95% of children immunised by the age of two.

Its figures show there are usually 100 cases of measles each year, but by mid-June this year, there had already been 159 cases.

Dr Hamish Meldrum, joint deputy chairman of the BMA's GPs committee told BBC News Online said: "We are in a situation where doctors really believe in MMR and its effectiveness and safety.

"Increasingly, we are finding doctors are being accused of saying what they are saying because there is money in it for them."

He said "informed dissent" could be the solution.

"If a patient, having had a course of treatment or a vaccination or a lifestyle change explained to them, says 'thanks doc, but no thanks', we could record that fact."

Independent advocate

Dr Steve Hajioff, a public health doctor in London said: "I'm convinced that the target payment system is acting as a barrier, rather than an incentive, in general practice.

"It's important that a GP is seen to be an independent advocate of patients' interests."

Liberal Democrat health spokesman Dr Evan Harris supported the move.

"It is right to end vaccination payment targets for doctors.

"Targets are counterproductive because they don't increase the number of vaccinations and are seen as unethical."