An undercover investigation has exposed the exploitation of illegal migrant workers on farms supplying Coles and Woolworths, as a Federal Government adviser called for reforms to stop the "systemic" abuse of foreign labour...

Dozens of illegal labourers on the farms said they were being underpaid by about $9 an hour to pick and package fresh produce that ends up being sold by Australia's big supermarkets...

"There is enough evidence to say that it is systemic," [...] "Significant numbers are really exploited."

Opposition Leader Bill Shorten called on the Government to deploy more resources to act "on these widespread and disturbing examples of exploitation"...

In a statement, Cutri Fruit said the company "would never knowingly exploit illegal workers from foreign countries".

"Our part-time and seasonal temporary workforce are engaged through contractors, as has been industry practice for decades" [...]

A Coles spokeswoman said the supermarket had referred the allegations about Cutri Fruit to the Fair Work Ombudsman and had launched its own investigation.

Woolworths said it required its suppliers to abide by employment and migration laws and would refer any allegations about a supplier breaching the law to relevant authorities.

Costco said it will stop buying Cutri Fruit until an audit of the company's practices is done.