NEW ORLEANS—Stephen Baldwin has sued fellow actor Kevin Costner over their investments in a device that BP used in trying to clean up the massive Gulf of Mexico oil spill.

The federal lawsuit filed in New Orleans on Wednesday by Baldwin and a friend claims Costner and a business partner duped them out of their shares of an $18 million deal for BP to purchase oil-separating centrifuges from a company they formed after the April 20 spill.

BP ordered 32 of the centrifuges, which separate oil from water, and deployed a few of the devices on a barge in June. BP capped the well in July and kept any more oil from leaking until the seafloor gusher was permanently sealed in September.

Costner's publicist, Arnold Robinson, declined to comment Thursday on the suit's allegations.

Baldwin and his friend, Spyridon Contogouris, owned shares in Ocean Therapy Solutions, the company that marketed the centrifuges to BP.

But Baldwin and his friend claim they were deliberately excluded from a June 8 meeting between Costner, his business partner Patrick Smith and a BP executive, Doug Suttles. At the meeting, the suit says, Suttles agreed to make a $18 million deposit on a $52 million order for the 32 devices.

Baldwin and Contogouris said they didn't know about the deal when, three days later, they agreed to sell their shares of the company for $1.4 million and $500,000, respectively.

Baldwin and his friend say they were entitled to shares of BP's deposit. Instead, their suit claims Costner and Smith "schemed" to use money from BP's deposit to buy their shares in the company.

"This action effectively robbed plaintiffs of a distribution that otherwise would have been payable to plaintiffs," says the suit, which seeks unspecified damages.

Costner and Suttles visited Port Fourchon in June to talk about the plan to use the centrifuges.

"It was designed to give us a fighting chance, to fight back the oil before it got us by the throat," Costner said at the time.