A payment system which gives GP surgeries money for how well they perform has not saved additional lives, a new study has found.
Research into the payment system used across the UK to pay GP practices is "yet to show clear patient benefits", the study concluded.
Experts from the universities of York and Manchester as well as the University of Michigan in the US set out to examine the pay-for-performance system used in the UK - the largest of such programmes in the world.
The Quality and Outcomes Framework (QOF) was introduced across general practice in the UK to improve patient healthcare and outcomes.
The QOF has been used across the UK since 2004 but last year Scottish ministers announced the country would no longer use the programme.
The programme increased GP income by up to 25%, dependent on performance on more than 100 quality of care indicators relating to management of chronic disease, organisation of care and patient experience. Almost £6 billion was invested in incentive payments during the first seven years of the programme.
The new analysis of the QOF, published in The Lancet, shows modest reductions in deaths, but no statistically significant declines in mortality rates for the chronic conditions targeted by the programme, including cancer, diabetes and heart disease.
The researchers conducted an evaluation of mortality statistics from 1994 to 2010 comparing countries that have implemented the programme with those that have not.
After analysing data from 27 high-income countries, researchers found that under the QOF, the mortality rate in the UK improved by less than four deaths per 100,000 people, depending on the condition. This is not a statistically significant improvement.
For chronic conditions not specifically targeted by the programme, the mortality rate actually increased by approximately 12 deaths out of 100,000.
The authors conclude: "Our results show that introduction of the QOF in the UK was not significantly associated with changes in population mortality for disease areas that were targeted by the programme. We recorded that the QOF was also not significantly associated with changes in mortality for disease areas that were not targeted by the programme.
"Extensive research into pay-for-performance programmes has yet to show clear patient benefits."
They added: "Programmes that use payments to physicians and health-care institutions to incentivise high-quality care have a strong foothold in several countries and are especially well developed in the UK and USA.
"Our research raises questions about whether pay-for-performance in other settings is a viable method to improve population health."
Tim Doran, professor of health policy at the University of York's department of health sciences, said: "Previous studies have shown that financial incentives paid to providers can lead to modest improvements in patient care, but the effects on patient outcomes have been variable, and in some cases care has suffered.
"These research results raise questions about the cost-effectiveness of pay-for-performance in healthcare, and about the best way to improve population health and life expectancy."
Lead author of the study, Dr Andy Ryan, associate professor in the school of public health at the University of Michigan, said: "The pay-for-performance programme is large and not only paid well but had quality indicators covering lots of disease areas. Our thought was if there was a programme that would make improvements on population health, this was likely to be the one.
"However, the outcome of this study is an indicator of how effective pay-for-performance is at improving patient outcomes."
Dr Chaand Nagpaul, chairman of the British Medical Association's GP committee, said: "The BMA has agreed with NHS England to review the future of QOF in England in order to find a less bureaucratic way of supporting GP practices who need to deliver care to their patients, especially those with long-term conditions.
"When it was first introduced, QOF did produce a useful way to enable practices to help patients to manage serious conditions such as diabetes, chronic lung conditions and heart disease. However, the QOF was undermined by increasing political interference which added needless paperwork and box-ticking. At the same time, practice funding was effectively clawed back, a move that has reduced the amount of investment going into frontline patient services."
Katherine Murphy, chief executive of the Patients Association, said: "GPs need to focus on all their patients and not just those patients where they can measure or record data and get paid for it.
"Giving doctors bribes to focus on specific conditions is morally wrong and ethically wrong. GPs must focus on patient care and outcomes - their priorities should not be compromised by financial incentives."
A Department of Health spokesman said: "We recognise GPs are under a lot of pressure and have already revised the QOF to remove 10 minute minimum slots for booked appointments, as well as reducing unnecessary paperwork for GPs so that they can spend more time with patients.
"NHS England has agreed to undertake a review of QOF in the coming year, to see how we can best manage the system for the future."