The move came after the High Court earlier this month rejected an attempt by the states and the union movement to have the Work Choices legislation declared unconstitutional.

The largest rally was in Melbourne, Australia's second largest city and capital of the state of Victoria, where unions estimated 60,000 people filed into the Melbourne Cricket Ground (MCG).

The rallies in all of the capital cities and hundreds of regional centers were linked by satellite to the MCG, the center piece of the union's protest campaign against the IR laws, which opposition and unions say undermine workers' rights.

Among the crowd in MCG were Federal Opposition Leader Kim Beazley and Australian Council of Trade Unions Secretary Greg Combet.

Beazley reiterated his commitment to repeal the laws if he won office and appealed to the crowd to throw out Prime Minister John Howard.

Beazley also promised to replace the laws with a "modern, fair and flexible system that Australians deserve."

An estimated 40,000 protesters participated in a procession through the city center of Sydney, Australia's largest city and capital of the state of New South Wales (NSW), bringing the central business district to a standstill.

Organizers estimate 150,000 people joined protests at 200 venues across NSW.

About 20,000 people gathered in Brisbane, Australia's third largest city and capital of the state of Queensland. Organizers said an additional 35,000 to 40,000 people gathered at smaller rallies at 42 other venues across Queensland.

About 7,000 people in Adelaide, capital of the state of South Australia, 3,000 in Perth, capital of the state of Western Australia, 2,000 in Darwin, capital of Northern Territory and 1,000 in the capital of Canberra turned out to take part in the protests.