Paul Corrigan, now an independent health consultant, says the BMA will push its anti-marketisation campaign when negotiations to make GP commissioning compulsory start.
'Andrew Lansley has made sure GPs are the absolute cornerstone of his policy without being certain they will do it,' he said. 'The GPC is in the absolute driving seat to make demands.'
His comments came as health campaigner John Lister said the BMA was making a 'historic mistake' by engaging with the DoH's White Paper reforms.
'I hope the BMA will take immediate steps to strengthen the very limited critique which seems to inform its current policy,' he wrote in a letter to the BMA. He said the BMA stance put a 'fig leaf of credibility' over Tory plans to privatise large swathes of the NHS.
GPC chairman Dr Laurence Buckman said he opposed the DoH's 'any willing provider' policy, but did not think the BMA could stop it.
'The GPC is not in the driving seat. The DoH is seeking our help but if we said we're not going to do any of it, it would just stop listening,' he said.
The BMA is still 'finding out what things mean', and responding to White Paper consultations, said Dr Buckman.
Mr Corrigan said the private sector was likely to be represented on the NHS Commissioning Board. He added that measures to ensure GPs do not overspend will limit their freedom.
Making GP consortia statutory bodies may mean they closely resemble PCTs, he added.