A third of GPs think their surgery is unlikely to remain open in 10 years' time, according to the poll of more than 500 GPs carried out by ComRes for the RCGP.
Around 95% or more GPs say that morale has decreased in the past five years, while fatigue and workload have increased.
A third of GPs have had to seek support, guidance or advice for work-related stress in the past two years, the poll found.
Ahead of chancellor George Osborne's spending review announcement on Wednesday, the RCGP called for a £750m annual increase in GP funding, rising to an extra £3.8bn annually by 2020.
The increase would deliver return the profession to the 11% share of overall NHS funding it received a decade ago, up from the 8.4% share it currently receives.
The increase in funding would pay for implementing the recommendations of the workforce commission led by Professor Martin Roland, which would cost an additional £1.66bn in general practice annually by 2019/20 in England, together with a further £709m for community nursing services.
This would deliver an additional 5,000 GPs, 5,000 medical assistants, 4,300 practice-based pharmacists, 1,000 physician associates, 2,275 practice nurses and 9,469 community nurses, the RCGP says.
RCGP chairwoman Dr Maureen Baker said: 'The results of our polls show that general practice is on a knife-edge, with GPs feeling that there is insufficient resourcing to deliver a five day service, let alone a seven day service, and two thirds of patients feeling that the high number of consultations being carried out by GPs is a threat to the standard of care they can provide to their patients.
'With the population ageing and growing in size, resulting in an increasing prevalence of serious long-term conditions, it is of little surprise that GPs’ workload has soared, while morale has plummeted.
'With this week’s spending review, the government has the opportunity to stop the rot, and start investing in a renewed general practice.'
Photo: Pete Hill