Media investigations show food supplied to Australia's biggest supermarkets and fast food chains comes from migrant workers in slave-like conditions.

The ABC has reported on widespread exploitation of people on working holiday visas, where some are made to work for less than half the legal wage.

At one chicken processing factory, the story showed migrants working 18 hours a day, seven days a week, with one worker saying he was forced to relieve himself on the job because he was not allowed to go to the toilet.

The Four Corner program said unscrupulous contractors were propagating black market labour by hiring migrants on expired or invalid visas.

Some are paid as little as $3.95 an hour.

Female workers described sexual harassment by supervisors at two separate labour hire companies, and there were even allegations that some were being encouraged to join organised prostitution syndicates across the country.

Federal Nationals MP Keith Pitt has called for strong government efforts to stop the exploitation of foreign workers.

“This is slave labour and in Australia that shouldn't happen,” he told reporters.

The Australian Greens say they will refer the reports to an existing Senate inquiry into the working visa system.

The footage from the story, a written transcript and responses from some of the groups featured in the damning ABC report are available here. 

UPDATE 06/05 - Reports say the Federal Government will begin auditing payslips and investigating claims of 417 visa abuse.