The DoH has remained adamant that it will not be prescriptive about consortia size. But the RCGP and GPC believe consortia should cover populations of about 500,000.
The view that there is a 'right size' has received a mixed response from policy experts. An alternative argument is also beginning to emerge, calling for consortia to be given the flexibility to grow over time.
The RCGP and the GPC say consortia covering populations of 500,000 will be able to pool risk, negotiate with acute trusts and attract high calibre leaders.
But Dr Judith Smith, head of policy at the Nuffield Trust think tank, says she would be 'cautious' about being too specific about the size of consortia as there is no 'one size fits all' solution.
Dr Smith says smaller GP consortia can commission services, but they would be restricted to those for long-term conditions, community health services, or a limited range of hospital care.
Not too small nor too big
However, Dr Smith also expresses concern about the formation of large consortia, as this would make it 'hard to distinguish them from PCTs', adding: 'The greater the scale of the consortia, the greater the trade-off you have over closeness to practices and communities.'
However, Dr Darin Seiger, chairman of Nene Commissioning, a practice-based commissioning group in Northamptonshire, says he agrees with the GPC and RCGP '100 per cent'.
He says Nene commissions care for around 672,000 patients and its size gives GPs 'absolute clout' in negotiating with the local acute trust.
'If we had four consortia going to negotiate with the acute trust then this would put them on a far less effective and influential footing,' he says.
Being a single unit means the acute trust 'cannot play us off against anyone else', he adds.
Dr Seiger added that locality groups within Nene mean it is no less responsive to local needs than small consortia would be.
'County-wide, transformational service redesign is done at consortium level, but we tailor transformations to the specific needs of the population in each locality,' he says.
Despite the successes in Northamptonshire, evidence in Cambridgeshire, where the PCT is piloting the allocation of real budgets to GP clusters, suggests an appetite for smaller-scale commissioning groups.
Here, GPs have decided on the size of the clusters. Two groups are set to launch next week, which cover populations of 70,000 and 40,000, and two more clusters, which will cover 52,000 and 74,000 people, hope to launch next month.
Meanwhile, a sense that GP consortia must be given the flexibility to evolve is also emerging. Speaking at a King's Fund event on commissioning this month, director of the DoH's policy unit Ian Dodge said there should be a 'dynamic ability' for good consortia to develop over time.
He said his comments are 'partly personal' because the White Paper consultation period has not finished.
Mr Dodge said: 'It appears to me that the right question is not about the right size and shape initially, it is about how dynamic the system is allowed to be over time.'
Dr James Kingsland, president of the National Association of Primary Care, agrees that consortium size is likely to be a 'dynamic, evolutionary process'. He says to formalise plans about consortium size now would be 'premature and naive'.
'Consortia take over full responsibility on 1 April 2013, and this is the beginning, not the end,' he says. 'The form may well change depending on local experience and need as well as through gaining experience on macro-commissioning.'
RCGP chairman Professor Steve Field says that it is an 'inevitability' that smaller groups will merge over time to form 'large groups with smaller sub-groups within them'.
'I wouldn't want to be prescriptive, but this is one possibility,' he says. 'We are looking for flexibility, basing everything on the needs of local patients.'