Thousands of union workers and supporters have descended to the streets of Melbourne to voice their outrage at what they see as a heavy-handed federal budget.

Unionists marched from the Trades Hall through the CBD to the Victorian Parliament buildings, standing firm and chanting in the faces of mounted and uniformed police officers.

Chief targets of their anger were cuts to government benefits, and big changes to higher education, training and health funding.

Fair Work Building and Construction has recently warned workers that they must seek permission from their employers to attend such rallies, or risk being fined.

The organisation says it has been investigating workers after previous rallies, and it can be expected that they will have noticed this one.

A stream of online support and photos from the events as they unfold have been shared under the banner #BustTheBudget

The following image was posted by Twitter user Sean Bedlam.