An emergency stability fund is urgency needed to halt the closure of up to 100 practices, the Royal College of General Practitioners (RCGP) has claimed.
The phasing out of the minimum practice income guarantee (MPIG) could affect a total of 1,700 practices.
Many of the surgeries served deprived inner city or remote communities, the RCGP has said.
Members of the college have said phasing out MPIG has “catastrophic” consequences because of a fall in funding in general practice.
In a study commissioned by the College, Deloitte recently estimated that, if current trends continue, funding will fall by a further 17% over the next three years to just 7.29%.
The RCGP wants an immediate cash injection for the practices facing imminent threat of closure or reductions in service – and a long term increase in general practice funding to 11% by 2017 at a time when patient consultations are set to soar by 69m to 409m consultations a year.
RCGP honorary secretary Professor Nigel Mathers said: "Without emergency funding, up to 100 practices will be forced to close, leaving 700,000 patients without a family doctor within months. If this is allowed to happen, it will have disastrous consequences for patients, their communities and the NHS.
"Last year, the government pumped £500m into A&E to stave off the winter crisis. A fraction of this would safeguard the future of these practices.
"It is vital that ministers also give a guarantee that no practices will close as a result of the phasing out of MPIG. The only way to ensure that general practice continues to be sustainable is for the four governments of the UK to ensure that its funding is increased to 11% of the NHS budget by 2017."