Almost half of Barnet's GP surgeries have been deemed unfit for purpose, according to the borough's Primary Care Trust (PCT).
The Department of Health has strict criteria for surgeries, with standards set for disabled access, the availability of hearing loops and building decoration.
According to Barnet PCT, 34 of the borough's 77 practices fell below minimum standards.
A survey by the medical journal Pulse revealed that this ranked Barnet as the third worst in London, above Bromley and Enfield.
Peter Packer, chairman of Barnet PCT's patient and public involvement forum, explained that many of the surgeries remained in converted houses, a legacy from when doctors often used to practise from home.
He said: "They are responsible for their own buildings and are reluctant to spend a lot of money on maintenance, and that includes disabled access. There wasn't the same focus then as there is now.
"The standards have improved but it depends on where you go in Barnet. The Government should really provide grants for GPs to update their premises. But they the figures should not have an effect on healthcare."
Barnet PCT's chief executive, Charles Hollwey, said: "Barnet PCT is the second largest in London, and as such has a greater number of GP premises.
"It is clearly our intention to invest in premises, which takes time, and it is unlikely that these figures take into account recent developments including the Bittacy Hill Surgery new larger premises and the Grove Mead Surgery benefited from a new building."