Primary care trusts should be allowed to “merge or demerge” into more successful commissioning organisations , rather than being swept away and replaced by smaller GP consortia, a think tank has said.

A report published by Civitas in conjunction with the Manchester Business School and shown to HSJ says there is little evidence that smaller organisations are better at commissioning than larger ones.

For example, it cites world class commissioning assurance results and the annual health check as evidence that larger and smaller PCTs can perform equally well.

The authors assessed PCT health check results for 2005-06 and 2008-09, and commissioning scores for 2008-09 and 2009-10, finding no relationship between size of PCT and performance on both governance and competence.

However, the right wing think tank warns that organisations any smaller than 100,000 - the smallest population covered by a PCT is around 90,800 - would not have sufficient resources to adequately spread the financial risk of commissioning and could lead to significant instability.

Report co author Kieran Walshe, professor of health policy and management at Manchester Business School, said: “It is likely that GP consortia will cover smaller populations than existing PCTs.

“There is little, if any, theoretical or empirical evidence to suggest this will lead to better commissioning - particularly when coupled with recent studies that suggest the transition will be costly and almost certainly result in at least a short term dip in performance.”

Professor Walshe cited health check scores after the reduction of 300 PCTs to 152 in 2006.

The percentage of merged PCTs rated good or excellent on service quality and use of resources fell between 2005-06 and 2006-07, while there was significantly improved performance in 80 PCTs that were not merged, he said.