The warning comes a month after GP revealed fears that 'vertical integration' could threaten the future of general practice (GP, 5 February).
Dr Michelle Drage, joint chief executive of Londonwide LMCs, believes all practices in the capital will be forced into 'poly-systems', with acute trusts shaping the services they offer.
After a two-month investigation by Londonwide LMCs, Dr Drage said PCTs in the capital face SHA pressure to shift hospital work to GPs working in polysystems - networks of NHS providers delivering a broad range of primary and acute services in the community.
London's PCTs also face pressure to 'vertically integrate' community services with acute trusts, she said. GP practices would become 'little more than chronic disease and outpatient management centres'.
Senior hospital managers have begun to make the case for taking control of practices. Robert Naylor, University College London Hospitals NHS Trust chief executive, has said the NHS can only stop inappropriate referrals if GPs are integrated with acute providers.
Dr Drage predicts London's 31 PCTs will be merged into five commissioning 'sectors' in 2011, bringing a 'further blurring of primary care'.
Most of the plans are set out in the NHS London report Delivering Healthcare for London - An Integrated Strategic Plan 2010-2015. Dr Drage believes the plans are based on advice from consultants McKinsey, but NHS London has rejected requests to see the advice.
Foundations trusts and the acute sector are now a greater threat to general practice than the commercial sector, said Dr Drage. She urged practices to 'pull together in networks and federate' to protect themselves.
Dr Andy Mitchell, NHS London medical director, said: 'We encourage all forward-thinking parts of the NHS to be prepared to initiate and run GP and community health services.'