Saskatchewan's fertilizer companies are the target of an anti-trust lawsuit in the United States.

Companies in the U.S. claim PotashCorp, Agrium and Mosaic worked together to drive up prices by slowing down production.

The three fertilizer companies are accused of pushing the prices up by 600 per cent in 2008.

Anti-trust rules exist under the Canadian Competition Act, prohibiting certain criminal offences including price-fixing and bid-rigging conspiracies, resale price maintenance, price discrimination and predatory pricing.

PotashCorp officials said the company pays close attention to anti-trust rules and hasn't done anything wrong.

"These are allegation that we believe are without foundation," said Bill Johnson with PotashCorp. "And they're allegations that we will defend ourselves against vigorously."

Fertilizer buyers said companies used the marketing company Canpotex as a way to share information.

The lawsuit alleges that as members of Canpotex, potash companies share private information that should not be shared.

A trial date has not been set.