Dr Pauline Brimblecombe, chairman of Cambridgeshire Association to Commission Health, (CACH) leads a consortium of 30 practices. She said commissioning in her area had only worked up to now because like-minded practices had formed consortia.
It would become a 'real issue' when practices that had originally opted out of consortia were forced to join, she said.
The health White Paper states that by 2012 all GP practices must be part of a consortium to hold a registered list.
Dr Brimblecombe referred to her area as 'Lansley-land' because it is often cited as an example of advanced GP commissioning by health secretary Andrew Lansley, whose constituency is nearby.
'We have formed clusters across PCT boundaries and local authorities with like-minded GPs. You have to join with practices you trust,' she told the National Association of Primary Care (NAPC) conference in Birmingham last month.
'We must have a right to eject or reject practices. I imagine the GPC will take this up with the government, but it might be that poor practices are taken over by consortia,' she said.
NAPC president Dr James Kingsland echoed the call, saying it was 'essential' consortia could force underperforming practices out of consortia.
But one GP, who wished not to be named, said his practice would be a 'liability' to any consortium because it was badly underfunded. He said the funding formula had left his practice underfunded and that previous practice-based commissioning allocations had been too small.
'We are not a failing practice - we are just badly funded. Are we going to get expelled from a consortium because we can't manage our budget?' he said.
GPC negotiator Dr Chaand Nagpaul said consortia should concentrate on clinical activity, rather than on how much individual practices spend. 'Concentrate on clinical activity and reducing demand,' he said.