Local and national policy that favours large practices will result in a ‘very unsatisfactory service', according to Andrew Rouse, a consultant in public health at Heart of Birmingham PCT.

Mr Rouse studied the performance of 10,055 UK practices according to their list size. A ‘clinical performance score' out of 62 was assigned to each practice based on QOF data.

 ‘There is a clear downward trend in clinical performance as practices got larger,' said Mr Rouse.

‘My findings strongly suggest that such a policy (away from small practices) may drive down quality of care significantly.'

Smaller practices (fewer than 10,000 patients) scored 35-36 points on average, while larger practices (over 20,000) scored 24-27 points on average.

Mr Rouse will present his findings to Heart of Birmingham PCT, which has been encouraging around 70 small and single-handed practices to move into 24 larger health centres since 2007.

Health secretary Andy Burnham told GP in January that single-handers were rightfully becoming ‘a minority' and across England GP leaders have accused PCTs of pressurising small practices.

Dr Peter Swinyard, chairman of the Family Doctor Association, said the perception of small practices being poor was ‘firmly ingrained' within the DoH.

‘We are certainly aware of the high quality of small practices. But it's very useful to be able to take research like this to the DoH and say ‘if you want quality, go small'.'

Mr Rouse believes the perception that small practices are poor is outdated.

‘There was reason to think that small practices were sub-standard, but that was in a different era - when you found little practices that couldn't use a keyboard. Once we get rid of those old-fashioned, small practices, it is not so clear.'

Mr Rouse said when there are fewer partners there is greater responsibility for the practice's performance.

‘In a huge practice, what is everyone's responsibility becomes no-one's responsibility. Nothing gets done,' he said.

But Dr Swinyard said doctors had a more personal relationship with patients in small practices, which meant they were happier to comply with QOF processes.

‘We don't have a problem with practices of any size. It's about getting to know patients and patients getting to know their doctor,' he said.