SUPERMARKET giants Coles and Woolworths are demanding fruit, vegetable, milk and meat suppliers complete "ethical trading audits".

Cranbourne vegetable grower Peter Schreurs said his family had received letters this month from both supermarket chains demanding they complete the audits.

"It includes environmental standards, labour rights, freedom of association, living wages, discrimination, immigration, bribery and health and safety," Mr Schreurs said.

"It will cost us money and will take time. We're about growing vegies, not about sitting in the office doing paperwork."

However a Woolworths spokeswoman said all the company's suppliers were now required to complete ethical trading audits.

"We've always been leaders in food quality and we have a responsibility to ensure our suppliers meet certain ethical standards."

In their Corporate Responsibility Report, Woolworths chairman James Strong and chief executive Michael Luscombe said their policy was based on ensuring "a good price does not come at the expense of human suffering".

"Ethical sourcing is not only about human rights. Increasingly, too, our community expectations have changed with respect to standards of animal welfare," they said.

Woolworths started demanding its international suppliers undertake ethical audits about two years ago. Last year, the company announced domestic suppliers would also be required to undertake ethical audits, with meat and poultry suppliers the first sectors asked to comply.

Coles spokesman Jim Cooper said the company had relaunched its ethical sourcing policy in December, to look at suppliers operating in "high risk" countries.

Ausveg chief executive Richard Mulcahy said he had contacted Woolworths after receiving complaints from Victorian and interstate growers concerned about the cost of complying with the audits.

"There's been no discussion with Ausveg on it," Mr Mulcahy said.

"There would have been some benefit in talking to us before they did this."