The bonus GPs get for seeing patients within 48 hours is set to rise by two-thirds next year.
The new GP contract came in last year
Surgeries which have met the target are being paid £3,875 on average, but that will increase to £6,200 in 2006.
The hike has raised patients' fears that more people could struggle to get advanced GP bookings.
The issue hit the headlines last week after the prime minister was harangued during a TV debate by people who could not book appointments in advance.
Patients have complained that GP practices have stopped taking advanced bookings because they have to meet a 48-hour target to provide appointments.
Tony Blair was told during BBC's Question Time on Thursday that patients were only being allowed to make appointments on the day or following day so GPs could keep slots free to meet the target.
Joyce Robins, co-director of Patient Concern, which has been campaigning against the target for the last year, said: "I don't feel this is in patients' interests.
"These targets just distort priorities, and our fear is that by going up so much the situation could become worse."
Family doctors can earn 1,050 points as part of a bonus scheme for achieving certain quality standards in a range of areas from access to disease management. For meeting the 48-hour target they get 50 points.
This year the average three-GP practice with 6,000 patients is being paid £77.50 for each point, but that will rise to £124 next year.
GPs get to keep the bonus, which is on top of their basic income, once running and staff costs are taken off.
The bonus scheme, known as the Quality and Outcomes Framework, was introduced as part of the new GP contract which kicked in last year. It is voluntary, but the overwhelming majority of doctors have signed up to it.
A spokeswoman for the British Medical Association said it would not lead to more surgeries refusing to take advance appointments for patients.
"The quality framework is really positive, although the 48-hour target is rather crude," she said.
"But the real problem is that there is a lack of staff, that is why surgeries struggle."
She also defended the rise, saying it was built in under the terms of the contract as the £77.50 figure was an underfunding.
Shadow Health Secretary Andrew Lansley said the Conservatives would make sure the bonus scheme ensured a quality service.
"We will abolish all political targets imposed on the NHS from Whitehall so that would include the 48-hour target in the Quality and Outcomes Framework."
Liberal Democrat health spokesman Paul Burstow added his party would also scrap political targets.
"The problem with the target is that it can be hit and GPs get their pay, but it misses the point, because patients don't get their appointment when they need it."
But Health Secretary John Reid said the answer was not scrapping targets, but to "reward" family doctors who see patients when they want to be seen.
He denied the problem with doctors not allowing patients to make advanced appointments was going to get worse.
The number of surgeries not offering such appointments fell from 12.4% in November to 3.6% in March, he added.