Research by Capability Scotland found that 40% of Scotland's 32 local authorities had no accessibility requirement in their taxi licensing regulations and had not kept pace with equality legislation.
It identified a rural/urban split in the approach of councils, with the majority outside cities having less stringent licensing criteria. This is a particular problem for wheelchair users in remote areas who are also less likely to have access to frequent and reliable public transport, the charity said.
Its report was published yesterday ahead of a Scottish Government consultation on taxi licensing, due to be published next week.
Richard Hamer, director of external affairs at Capability Scotland, said there had been little improvement since the charity's last taxi survey in 2009.
He said: "The Equality Act 2010 places a positive duty on local authorities to proactively consider how disabled people will be affected by their activities, including their licensing function. Many local authorities are failing to act on this obligation when it comes to the licensing of taxis."
According to Scottish Government figures, 46% of the 10,000 licensed taxis in Scotland are accessible to wheelchair users, compared to only 2.6% of the 10,000 licensed private hire cars.
A spokesman for the Convention of Scottish Local Authorities, the umbrella body for councils, said: "Councils take their duties in relation to equalities and disabilities extremely seriously."
A Scottish Government spokeswoman added: "The Scottish Government will look at opportunities to work with Capability Scotland to encourage best practice in local authority accessibility policies."