The GP contract was introduced in 2004
The GP contract introduced in 2004 has helped reduce gaps in care between wealthy and poor areas, a study says.
Researchers looked at the performance of over 7,000 GP practices over the first three years of the deal.
They found standards of care in less wealthy areas - which had tended to be worse - had improved at a quicker rate than elsewhere, the Lancet reported.
The Manchester University team said the extra money and performance-related pay in the contract had driven up care.
The new deal was introduced across the UK in 2004. It meant about a third of doctors' pay was linked to performance in a range of key areas.
These are judged over 100 indicators covering things such as waiting times and disease management.
The researchers looked at 48 indicators covering conditions such as heart disease, diabetes, epilepsy and high blood pressure.
They divided the practices they looked at in England - although the findings can be applied to the whole of the UK - into five groups according to the levels of deprivation.
In year one, the most deprived areas hit the targets 82.8% of the time, compared to 86.8% for the most affluent areas.
By the third year, the poorest areas achieved 90.8% of the indicators on average, while the richest areas achieved 91.2%.
It meant the gap narrowed from 4% to less than 1%.
The findings come after the contract has been criticised for costing too much - average GP pay increased by a third in the first two years to top £100,000 a year - and harming out-of-hours care.
Lead researcher Dr Tim Doran said the results were "good news", but the contract still had to be judged in context of the wider problems.
He added: "Doctors would say that the extra money in the contract is allowing them to provide the level of care in the deprived areas that they could not before.
"Another interpretation is that the poorer performing doctors were capable of doing what they are now doing and have been pushed into it by the incentive of money.
"I guess it is probably a bit of both."
The study comes as separate research found the contract meant improved care for patients with heart disease.
The report in the journal Heart compared GPs in Northern Ireland, which is covered by the UK deal, with those in the Republic of Ireland, which does not have performance-related pay.
It found family doctors in Northern Ireland were better at controlling blood pressure and cholesterol levels.
A Department of Health spokeswoman said the contract was working and the government was now looking to build on it.