Women are being sexually assaulted by taxi drivers preying on lone females leaving clubs and parties, specialist doctors who examine rape victims have warned.

Passengers and drivers: Have a taxi story? Contact John Silvester

Research by the Victorian Institute of Forensic Medicine shows most victims - the majority of them ''cognitively impaired'' - have been picked up in the early hours of Saturday and Sunday mornings.

In 25 cases over a three-year period, the institute found 21 victims who were affected by alcohol or drugs and another two were intellectually disabled. The condition of the remaining two was not recorded. All were aged 17 to 39.

Public Transport Minister Terry Mulder said he had asked the Taxi Services Commission to work with police on the problem.