Professor Calum Paton, a health policy expert at Keele University, told the House of Commons health select committee that the strength of local primary care is key to the success of commissioners.
But he said government fears over conflicts of interest mean GPs will have little power to influence local primary care services. If consortia were run by clinicians of all types, not dominated by GPs, it would help prevent conflicts of interest, he said.
'GP consortia can't do local commissioning of primary care because it's a conflict of interest for them. But there shouldn't be one group taking responsibility for all commissioning,' said Professor Paton.
'The conflict of interest is a conflict of the government's making and they then have to drive a coach and horses through other potentially effective arrangements,' he added.
The abolition of PCTs, with GP contracts held centrally by the NHS Commissioning Board, could mean 'a potential lack of commissioning of primary care services', said Professor Paton.
MPs from the committee asked policy experts whether the centralisation of GP contracts was part of a 'hidden government agenda' to procure more GP services from private providers.
Nigel Edwards, acting chief executive of the NHS Confederation, said it was unlikely there was any hidden agenda but the Health Bill 'certainly does make it easier to do so'.
Later, Dr Ron Singer, president of the Medical Practitioner's Union, warned the committee that a proliferation of privately run GP practices could lead to consortia made up entirely of private sector providers.
Such consortia would have 'a confused allegiance to either private employer or NHS', said Dr Singer.