Some NHS family doctors are earning more than £100,000 a year - up to 30 per cent higher than estimated by the British Medical Association.

The findings raise concerns about how new "paid by results" contracts for GPs, which were designed to help deprived areas, are being implemented.

Doctors' leaders accused the Government of using the contracts to divide GPs and undermine the power of the BMA.

The British Medical Association disputed the figures, which were taken from a survey of 5,000 GPs by the Association of Independent Specialist Medical Accountants (Aisma). The average GP earned £79,509 last year, according to Aisma - almost £20,000 more than the BMA's estimate of £61,000.

In 141 practices, GPs earned more than £100,000 a year, the survey found. In 2001 only 91 practices had doctors earning more than five figures.

The survey found big gaps between the money earned by GPs on traditional, national contracts and those on Personal Medical Services contracts, which are negotiated locally. Doctors on the PMS contracts earned almost a third more in 2002.

The PMS contracts were introduced in 1998 with the aim of encouraging more GPs to work in deprived areas with a shortage of doctors. They are designed to pay GPs for providing extra services, such as drugs and alcohol counselling. Bob Senior, of Aisma, said: "They are getting paid more for delivering more."

The PMS practices are also dealing with more patients - 2,046 per full-time GP, compared with 1,942 per doctor on a national contract.

One in four GPs currently work under PMS contracts, although the Government wanted one in three to be signed up by last year.

But Dr Peter Holden , of the BMA, said: "Aisma tends to represent the high-earning GPs, and they have taken into account non-NHS earnings such as the payments doctors get for providing services such as police work." He said the average PMS doctor earned £66,000 and a doctor on a traditional contract earned £58,000.

The salary findings come at a crucial time for doctors on traditional contracts, which have been re-negotiated by the BMA and the Government. Dr Holden, a negotiator on the new contracts, accused the Government of trying to undermine the BMA by "bribing" doctors into the PMS camp.