The union representing rail workers is pushing for permanent staff to be on board trains.

The Rail and Maritime Transport Union is hoping an inquiry into an attack in Auckland where a train was 'graffiti bombed' will demonstrate they are needed on board for public safety.

Spokesman John Kerr said the presence of the on-board Train Manager played a vital part in preventing the weekend incident becoming more serious.

"We think this attack on Sunday demonstrates the absolute necessity for having permanent train staff on the trains for passenger and public safety."

Kerr said there are moves to remove onboard train managers from next year.

"We believe that the absolute fundamental need to have on board staff on trains for public safety will be demonstrated when that report is completed."