One in 10 GPs believe their practice is at risk of closure in the next 12 months because of underfunding, workload or recruitment problems, according to a GPonline opinion poll of 298 GPs.
Many more GPs are aware of struggling practices in their local area - 41% of respondents said they knew a neighbouring practice that was at risk of closure in the next year.
GP leaders warned that NHS England must do more to deliver rapid bailout funding to prevent the collapse of practices across the country.
GP practice closures
The closure of one in 10 of the 7,500-plus GP practices in England - which have an average list size of around 7,000 - could leave 5.25m patients looking for a new family doctor.
The GPonline poll findings echo results of a huge BMA poll of more than 3,000 surgeries earlier this year which found that 10% of GP practices were financially unsustainable. NHS England officials have also declared that in parts of the country as many as one in five practices are 'vulnerable'.
GPC chairman Dr Chaand Nagpaul warned in June that GP practice closures had hit record levels over the previous year, with 201 forced out of business. But the poll suggests that this figure could be dwarfed by closures in 2016/17.
Not all practices forced to close will be lost to patients - a GPonline investigation earlier this year found that of 402 practice contracts terminated between 2013 and 2016 around two thirds were merged with other practices, with the surgery potentially remaining open under new management.
But the remaining third were closed altogether, leaving patients to register with other practices in their area.
Senior NHS officials have warned that the collapse of practices in a local area risks triggering a 'domino effect' that destabilises others.
Even GP practices rated good or outstanding by the CQC can be 'fragile' and at risk of falling over if they lose a senior partner or practice manager, NHS England head of primary care commissioning Dr David Geddes told an event at the RCGP conference last month.
GPC deputy chairman Dr Richard Vautrey said: 'These findings echo those of those of the BMA, which suggest that more and more practices are set to close and more and more patients are set to lose their local GP service.
'Commitments by NHS England of funding to bail out hospital trusts, or to provide appointments at weekends, or invest millions of pounds for IT developments demonstrates that resources are available, but they are not yet being spent where it they are most needed - core general practice.
'It's essential that governments across the UK speed up the delivery of funding and support for general practice.'