Separating commissioner and provider functions, as advocated in world class commissioning, may damage the efficiency of the health service, a leading academic has claimed.

An analysis of research on commissioning models across the world by Chris Ham of Birmingham University's health services management centre has brought to light "major obstacles" to the efficient operation of systems that separate commissioner and provider roles.

It may be better for commissioners and providers to integrate and take decisions together rather than in isolation, the report, Healthcare Commissioning in the International Context: lessons from experience and evidence, suggests.

Professor Ham told HSJ that no country that had the split approach had produced world class commissioning across the board.

He said most primary care trusts were struggling to recruit commissioners with the right skills and warned there was no guarantee the approach would pay for itself.

"Whenever you run a purchaser-provider system based on the market, there will be quite high translation costs associated with that to negotiate and monitor contracts," he said. "So there must be sufficient benefit coming out of that contracting system to justify the cost of running it that way, and we don't know yet whether that can be achieved."

The study came as the latest quarterly survey of GPs revealed that half of practices rate primary care trust support for practice based commissioning as "poor" and that the number of practices rating PCT support as good has dropped from 42 to 40 per cent. And, while 41 per cent of practices have commissioned a service using PBC, more GPs disagreed with the statement that PBC has improved patient care than agreed with it.

PCT Network chair David Stout said it was crucial trusts managed GP expectations about PBC.

A Department of Health spokeswoman said all integrated care models required strong commissioning and clinically led integration initiatives. She said: "Through the next stage review, we are considering how best to develop the commissioning and provision capability of the NHS further."