The total number of patients registered with GP practices in England increased by 1,116,636 between January 2014 and January 2016, the analysis of data published by the Health and Social Care Information Centre (HSCIC) reveals.
Practices in nearly one in 10 of England's 209 CCGs have seen patient numbers rise by an average of 4% or more over the past two years, GPonline has found.
GP leaders warned that practice funding had failed to keep pace with the rise in patient numbers, and that rising pressure put the safety of patient care at risk.
GPonline revealed last week that GP practices had maintained high levels of patient satisfaction despite rising pressure.
Of 18 CCGs that saw numbers of registered patients increase by more than 4% over the two-year period, 13 are in London.
Patient numbers rose fastest in NHS Birmingham South and Central CCG, which saw an 18.7% increase between January 2014 and January 2016 - although the figures are inflated by around 10 practices joining from a neighbouring CCG.
NHS Central London (Westminster) CCG saw the next largest increase, up 8.1% - with more than 16,000 extra patients joining practice lists over the two-year period. The increase is equivalent to almost 450 extra patients per practice in the area.
In NHS North Manchester CCG - the third-fastest growing area - numbers of registered patients rose 5.3%.
Meanwhile, the data suggest that significant numbers of practices have closed or merged over the two years assessed by GPonline.
GP practice closures
In January 2016, 7,712 GP practices are listed in the HSCIC data, compared with 8,015 in January 2014. The data also suggest that practice size is increasing, with 7,087 the average practice list in January 2014, compared with 7,461 in 2016.
GPC deputy chairman Dr Richard Vautrey said: 'The rise in the number of people practices are having to cope with is not matched by an increase in investment to expand the number of GPs, nurses and other members of the practice team, nor sufficient support to expand practice premises.
'Patient care will suffer as a result unless NHS England urgently steps up funding increases. Many practices are now bursting at the seams and will increasingly struggle to be able to take on more patients even if they wanted to. The £1bn promised for premises must therefore be spent on premises development and not diverted to other politically motivated projects.
'The growing size of practices and the falling number of practices follows the trend in recent years as practices merge and smaller practices close. However it might also be fuelled by the increasing number of GPs even in bigger practices who are quitting the NHS and handing back their contracts.'