An estimated 350,000 patients were forced to move to a new GP surgery over the past year due to closures, figures suggest.
Around one in five closures were due to branches merging with others nearby, but many were due to practices closing altogether.
Eighteen GPs closed in London, affecting an estimated 61,000 patients, according to the data.
Dr Michelle Drage, chief executive of Londonwide Local Medical Committees, said staff vacancies and doctors approaching retirement were also having an impact.
She said: "Throughout this time we have consistently found that a third of practices are carrying GP vacancies and two fifths have impending retirements - the workforce crisis that threatens the stability of so many London practices is not going away.
"The coronavirus response poses new threats to viability, with infection-control measures and increased demand further stretching resources, and lack of full reimbursement of pandemic-related expenses squeezing finances."
A spokesman for NHS England said: "While this represents a very small proportion of practices, in some cases surgeries have merged with a nearby practice and in other cases a partner may have retired.
"The expansion of primary care networks is ensuring greater availability of the right kind of appointment for patients - whether face to face or remote - and support for constituent practices."
Additional reporting by PA
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