5000 May Day marchers brave rain in WA

The federal government is ignoring demands for job security from ordinary workers in favour of pushing through $65 billion in corporate tax cuts, the head of the peak trade union says.

Australian Council of Trade Union secretary Sally McManus told a 5000 strong crowd of May Day marchers in Fremantle that protections for working people had been "eroded".

"People in Perth are telling us what workers across Australia have been telling us. The rules are broken and something needs to change," Ms McManus said.

The theme for this year's May Day is "Change the Rules," with unions across Australia holding 12 days of action to support changes to wages and demand more permanent, full-time work.

Ms McManus accused the Turnbull government of ignoring the concerns of the community in favour of a $65 billion tax cut for "big business and the banks".

And workers were failing to get fair pay rises, she said.

Unions WA secretary Meredith Hammat said the next federal election will be decided in WA, citing five coalition marginal seats which could be up for grabs.

People understood employers who relied on casual and temporary overseas workers were the cause of "rising" work insecurity, she said.