BP is using "coercive tactics" to force victims of the 2010 Gulf of Mexico oil spill to agree to final settlements with its claims fund, lawyers suing the company said Monday.

BP set up the $20 billion Gulf Coast Claims Facility to pay emergency, interim and final payments to the victims under the provisions of the U.S. Oil Pollution Act. Lawyers for property owners, businesses and others claiming harm say victims have been forced to sign releases for inadequate payments because they could no longer afford to wait for full compensation.

A federal judge should appoint a special master to oversee the process, the lawyers said in papers filed Monday in federal court in New Orleans. They also asked U.S. District Judge Carl Barbier, who is overseeing the litigation, to "suspend the effectiveness" of any releases signed by spill victims who received money from the fund.

BP has not commented

"BP has failed to comply with the letter and spirit of OPA, a law designed to provide an interim claims process," according to the filing. The primary function of the claims process has been to convince victims "that the only compensation available is a minimal set amount that comes with a full release attached," the lawyers said.

"The GCCF will respond to the filing in due course," Kenneth Feinberg, administrator of the BP fund, said in an email. "We have paid interim payments to over 20,000 claimants and there are over 40,000 final payment offers outstanding. The GCCF has so far paid out over $250 million in interim payments and $4.8 billion in total claims."

Spokesmen for London-based BP didn't immediately respond to email or phone messages seeking comment.

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In April, after four Gulf state attorneys general asked the judge to intervene with the fund, Feinberg said Barbier had no legal authority to oversee the BP claims process. The state officials asked Barbier to conduct an independent audit and hold public hearings on the results, as they claimed Feinberg's fund was stalling interim payments to pressure "economically desperate" victims into settling too soon for too little.

"Even if it did have legal authority," imposing the court's supervision over Feinberg's fund would "divert resources and chill the ability of GCCF personnel to work expeditiously without fear of running afoul of an independent auditor and a court-imposed evidentiary hearing," David Pitofsky, Feinberg's lawyer, said in an April filing.

Last week, Feinberg agreed to commence an independent audit of the fund before the end of this year, after U.S. Attorney General Eric Holder requested one following a face-to-face meeting over government concerns about delays in payments to spill victims.

BP faces more than 350 lawsuits by thousands of property owners, fishing interests and tourism businesses claiming harm from the worst offshore oil spill in U.S. history. The spill resulted from the April 2010 explosion and sinking of the Deepwater Horizon rig while drilling a BP well off the Louisiana coast.