Analysis by GPonline of NHS Digital data on registered patients found that 254 GP practices listed on 1 April 2017 no longer appear in figures for 1 April 2018.
GPC chair Dr Richard Vautrey said that without an urgent injection of funding to maintain general practice, 'the domino impact of general practice closures will increase'.
The figures follow warnings from GP leaders earlier this week that most practices across the country are operating 'on the edge of viability'. In March, meanwhile, GPs at the 2018 LMCs conference in Liverpool called the rate at which partners were being forced to hand back their contracts a 'national disgrace'.
The analysis by GPonline shows that small practices are more likely to have been affected, with an average list size of 3,887 among practices that appear to have closed or merged - almost exactly half the average 7,785 practice list size on 1 April 2017.
The loss of smaller practices saw the average list size of GP practices climb to 8,154 on 1 April 2018 - a 5% increase compared with 12 months earlier.
Large practices were also caught up in changes, however - the largest practice that appears to have closed or merged had a registered list of more than 19,000 patients. A total of 13 practices had list sizes in excess of 10,000 patients.
Dr Vautrey said: 'List sizes are increasing as a result of practices merging together as well as some closing, leaving patients to move to other practices.
GPs at breaking point
'In some cases this is planned, as smaller practices decide to work with others for mutual support, but all too often in recent years this has happened because practices have reached breaking point, with other practices in the area picking up the pieces and doing what they can for local patients.
'This does though mean patients are left travelling further for care and the problems that undermined one practice are passed to another that also may be impacted by the same lack of funding and recruitment problems. There is an urgent need to invest in general practice properly otherwise the domino impact of practice closures will increase.'
The BMA has warned that even with investment promised through the GP Forward View, general practice will receive £3.4bn less than the share of NHS funding it needs by the end of 2020/21.