Mr Britnell, former DoH director of commissioning and now head of health at consultancy firm KPMG, said GP consortia should be 'public-private joint ventures'.

To work effectively, they need to be large, he said. 'It will not work if we create 500 cottage-sized commissioning bodies. It is possible if we create integrated care organisations, and public private joint ventures.

'The most agile PCT chief executives should be thinking about aggregating - it isn't possible for 152 organisations to be world-class, and it will not work with 500.'

Although health secretary Andrew Lansley has said he will not dictate how large consortia will be, the recent White Paper says they should be 'smaller than PCTs'.

Dr Darin Seiger, chairman of Nene Commissioning, one of the UK's most advanced practice-based commissioning groups, said the new consortia had to be large to be financially stable.

'Large consortia can absorb variation in activity year on year. Small consortia only need a tiny variation to tip them over the edge,' he said.

But Dr James Kingsland, president of the National Association of Primary Care, argued that he had seen 'fantastic' work done by small consortia. 'We've seen dramatic changes in patient care from groups covering 30-40,000 patients,' he said.

Smaller consortia may have to take part in 'risk-pooling' with other groups when budgets transfer to GPs, he said.

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