Tram services will be slashed on some of Melbourne's busiest routes next month, leading to longer wait times and increased crowding.

Tram frequency will be reduced on six of Melbourne's busiest tram routes when the timetable changes on May 1. Public transport advocates and the Opposition have slammed the move by the Andrews government.

There has been an increase in the number of serious injuries on Melbourne's trams. Credit:Joe Armao

The government has issued no public warning about the looming cuts, which will hit night-time services hardest, but also includes the loss of some services in the morning peak.

A press release issued by Public Transport Minister Jacinta Allan on March 28 claimed there would be "no reduction in services to Brunswick and Coburg", but The Age can reveal routes to those rapidly growing northern suburbs do face cuts.