A commuter was assaulted after he stood up for three Muslim women who were subject to a vile racial and bigoted attack on a packed Melbourne train.

Jason Cias, 36, was travelling home from work in the city on the Craigieburn-bound train on Friday, May 15, when he saw two tradesmen vilifying three women - one older and two who appeared to be in their 20s - who were wearing headscarves.

The train had pulled out of Melbourne Central station about 3.15pm when the unprovoked abuse began after one of the younger women sat next to the tradesmen.

"One of them made reference to her headscarf, saying 'You shouldn't be wearing that shit in Australia'," Mr Cias said.