New York (AFP) - Swiss food giant Nestle is being sued in the United States for allegedly knowingly allowing its Fancy Feast cat food to contain fish from a Thai supplier that uses slave labor.

Pet food buyers who filed the class action lawsuit on Thursday in US federal court in Los Angeles seek to represent all California consumers of Fancy Feast who would not have purchased the product had they known it had ties to slave labor.

According to the lawsuit, Nestle works with Thai Union Frozen Products PCL to import more than 28 million pounds (13 million kilograms) of seafood-based pet food for top brands sold in the United States, and that some of the ingredients in those products came from slave labor.

Men and boys, often trafficked from Thailand's poorer neighbors Myanmar and Cambodia, are sold to fishing boat captains who need crews aboard their ship, the complaint said.

It spoke of shifts of up to 20 hours a day with little or no pay, and beatings or even death if the work is deemed unsatisfactory.

"By hiding this from public view, Nestle has effectively tricked millions of consumers into supporting and encouraging slave labor on floating prisons," said Steve Berman, managing partner of the Hagens Berman law firm.

"It's a fact that the thousands of purchasers of its top-selling pet food products would not have bought this brand had they known the truth -- that hundreds of individuals are enslaved, beaten or even murdered in the production of its pet food."

Nestle lists protection of human rights as one of its Corporate Business Principles.

But "Nestle has failed to uphold its responsibility to ensure the absence of slave labor in its supply chains -- and even worse, Nestle not only supported these human rights violations, but forced consumers to unknowingly do the same."