Responding to questions on health policy from GP newspaper, Mr Lansley said the Conservatives recognised the need to shift NHS work into the community.
But he said the government and PCTs currently planned to move 'huge volumes of out-patient and A&E cases'.
The plans were based on incorrect financial assumptions, and GPs have neither the capacity nor the facilities to take on the extra work, he suggested.
A Tory government would ditch current proposals for moving work into primary care, and hold local consultations to gauge what could feasibly be transferred, Mr Lansley said.
GPC negotiator Dr Chaand Nagpaul warned: 'You can't just transfer unresourced work. The proposal to consult is sound, but we need evidence that there will be a transfer of commensurate resources.
'We have seen a significant shift of work from secondary care that is not resourced. General practice is not a limitless sponge to absorb this workload.'
Northumberland LMC medical secretary Dr Jane Lothian said any consultation must assess capacity, but also define processes to help practices set up services that took work out of hospitals.
She said GPs often struggled to attract funding for new services while hospitals could set them up on a whim.