A fourfold variation in demand for GP out of hours services has emerged in the first detailed data to allow for comparisons between areas.

The Primary Care Foundation has launched its “Benchmark” online tool containing data on services in 104 primary care trust areas. Information including the proportion of patients referred to hospital, assessment times, and patient satisfaction is recorded.

It is the fourth year the data has been collected but the first time it has been released online in this format.

The results, based on data from 2010-11, showed there were 50 “cases” of out of hours service use a year per 1,000 population in major conurbations such as London or Manchester, but more than 200 per 1,000 residents in smaller population centres such as Doncaster and Torbay.

The foundation said this could be because cities tend to have younger populations and more alternative services such as walk-in centres and hospital emergency departments.

However, the report said that variations in some performance measures were “wider than seems to be explicable” by external factors such as geography or demographics. “Although services are improving, some appear to have more catching up to do – with response times in a few services being comparatively slow.”

The report also highlighted inconsistencies in PCTs’ monitoring of out of hours services at board level. “A number of providers too have commented on how narrowly the service is looked at by commissioners,” it said.

Cost per head of population varied from less than £5 in Southwark to more than £14 in Gloucestershire.

However, foundation director Henry Clay said variations in cost were coming down.

“Out of hours services have been under intense scrutiny for some years following a small number of disastrous incidents,” he added.

“The publication of this report and the online tool not only provides a way of comparing services but also demonstrates a clear commitment to openness in sharing this level of detail.”

The foundation also suggested that patients did not necessarily prefer a face-to-face service.

Doncaster’s service, which has the highest proportion of cases where patients were given advice over the phone, was highly rated by patients.