The total number in substandard accommodation has risen from 306 in March 2004 to 517 in March 2005.
Minimum standards take into account issues such as ease of access, equipment in treatment rooms and the comfort of waiting rooms.
Health minister Jane Kennedy revealed the figures for London in a written parliamentary answer last week. The DoH said 657 premises in England were substandard in 2004, but that figures for 2005 were not available.
If the trend for London has been matched elsewhere as the GPC suspects, more than one in 10 premises in England would be considered substandard.
The DoH figures showed that none of the 58 surgeries in Havering PCT met minimum standards, and only three in Lewisham.
In nine of London's 31 PCTs, more than half of surgeries were substandard.
The GPC has consistently called for more premises funding and carried out a survey to support its claims for more money (GP, 24 February).
Dr Eric Rose, chairman of the GPC's premises finance subcommittee, said early survey indications were that problems in London were indicative of the national situation.
However, he said: 'In London, site value is high, so you can't obtain land on which to build improvements.'
Ms Kennedy admitted that there were 'many GP premises across London below minimum standards'.
'Judgments for some of those standards are subjective, which by their very nature might lead to some PCTs reporting higher levels of premises that do not meet minimum standards, than other PCTs with similar premises,' she said.
A DoH spokesman confirmed that being substandard 'might involve something as straightforward as provision of nappy changing facilities'.
'Compliance with the Disability Rights Bill has become important, so we could be seeing more substandard practices due to increased awareness of the need for disabled access,' he said.
Dr Rose agreed that disability legislation was partly to blame, but said the rate of change in general practice was a more pertinent problem.
'When you expand, what you do to the old premises might no longer be enough,' he said.
Practices' premises below minimum standards:
Richmond and Twickenham 77%
Barking and Dagenham 70%