Thousands of protesters have blocked traffic outside Victoria's Trades Hall in protest at harsh federal budget measures.
The crowd, which includes a large number of construction workers and unionists, blocked Lygon and Russell streets before marching to parliament on Thursday morning.
Protesters are chanting "they say cut back, we say fight back" in response to federal budget cuts.
Speakers at the rally will include Australian Manufacturing Workers Union Victorian secretary Steve Dargavel.
Rally organisers said the column of protesters that arrived at Spring Street, outside parliament house, stretched as far as Bourke Street, more than one kilometre away.
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Construction, Forestry, Mining and Energy Union national secretary Michael O'Connor said the federal coalition government was attacking jobs.
"We have never before seen a government try to destroy the jobs of Australians like this government has," he told the crowd.
"They are trying to change our commitment to a fair go, our commitment to justice, our democratic right to organise. They think they are going to get away with it. We say they ain't."
United Voice Victorian secretary Jess Walsh said workers were angry.
"We're angry at a government that wants to make us work harder and work longer for less money and we are here today because we deserve better, and we are here on the streets with you today because we are ready to fight," she said.
