Melbourne tram has been clocked speeding by police - the first time a driver has been caught by a radar gun.

A traffic policeman with the laser radar gun clocked the tram at 57kph in a 40kph zone on Malvern Road, Prahran, shortly after 7.30am, a police spokeswoman said.

The officer intercepted the tram and issued the driver with an on-the-spot fine, she said.

"It's the first time that a member has detected a speeding tram. He said it was quite unusual," she said.

The officer, from Stonnington traffic management unit, said the tram driver was "co-operative", the spokeswoman said.

"There was no animosity," she said.

The driver was fined $215 and will lose three demerit points from his normal driver's licence.

Yarra Trams spokesman Colin Tyrus said the driver also would be counselled by the company and would be subject to an internal disciplinary process, but would not disclose the process for privacy reasons.

"There's no exception for tram drivers to the speed limit," Mr Tyrus said.

"This is something that Yarra Trams regularly refers to in refresher training and initial training, that drivers are required to observe the road laws of the state of Victoria, and that includes speed limits."