PCTs are currently handing over control of community services to providers such as acute trusts or social enterprises under the Transforming Community Services plans, originally published in January last year.
But GPC chairman Dr Laurence Buckman said that due to financial pressure on trusts, the reforms were being implemented earlier than expected and without local consultation.
'This flouts every one of the Darzi principles. Decisions are being made, without GPs' input, very fast,' said Dr Buckman.
'Very soon, GPs will notice the service from their community matrons, district nurses, and physios will either vaporise or turn up in some other guise where cost has been reduced. If patients don't notice, GPs sure will,' he said.
Dr Buckman added that community nurses will be 'grabbed to work in hospitals' if they are employed by acute trusts.
Karen Reay, national officer for health at Unite, said, 'there were huge concerns over staff pay and conditions.
'In the 1980s, community units became part of acute units. Whenever resources got tight, money was pulled away from the community to meet acute targets,' she added.
The GPC is working with other unions and the Royal College of Nursing to help staff affected, said Dr Buckman.
GPC negotiator Dr Peter Holden said GPs working in community hospitals are already being offered new contracts with non-NHS organisations that could compromise benefits they have earned.
'Many GPs will have worked in community hospitals for 25 years. If you change employers and contracts, you may lose that 25 years of redundancy pay.
'It's inevitable GPs are going to change employers but that doesn't mean you need a new contract,' he said.
Dr Holden advised GPs to speak to an industrial relations officer at the BMA before signing new contracts.
A DoH spokeswoman said NHS staff transferring to other providers would have terms and conditions protected.
Transforming Community Services
Fears outlined by the GPC over the shift of community services out of PCTs include: