LOS ANGELES – A coalition of environmental groups filed a federal lawsuit Monday against Southern California's anti-smog agency accusing it of unlawfully allowing companies to pollute by selling them invalid emission credits.

The lawsuit accuses the South Coast Air Quality Management District of selling the bogus credits “to countless polluting facilities” for nearly two decades.

The credits are required by state and federal law for companies seeking to expand operations and emit more pollution. The conservationists charge that the air district's cache of emission credits was used up long ago, but that it sold companies bogus credits allotted for public service projects.

The agency covers Orange County and parts of Los Angeles, San Bernardino and Riverside counties.

“Why is the agency created to protect the air so actively trying to pollute it?” said Tim Grabiel, a staff attorney for the Natural Resources Defense Council, among the groups that filed the lawsuit.

The coalition accuses the agency of violating the federal Clean Air Act, which requires credits to be enforceable, quantifiable and permanent. The group wants a court to declare that the district violated the act and wants an injunction prohibiting the district from distributing invalid credits.

Several calls for comment to the district were not returned Monday afternoon because the organization's media office was closed.

Others groups that filed the lawsuit include the Coalition for a Safe Environment, Desert Citizens Against Pollution and Communities for a Better Environment.

On July 28, the same group won a related court victory regarding how the agency developed its air credits. A Los Angeles Superior Court judge found that local officials had not done an adequate environmental and health analysis before deciding to sell credits to energy companies for far below market value. The decision threw a wrench into plans for more than a dozen new power plants in Southern California.

The credits in question were part of a special supply of pollution credits that were supposed to be used for public services such as the construction of schools or hospitals even if they add to the region's pollution. Instead, the district sold the credits to energy companies for $420 million.

Angela Johnson Meszaros, an attorney for Desert Citizens Against Pollution, compared the regional agency's activities to a bank giving out counterfeit dollars.

“We say you can't give money to power plants,” she said. “Then we start looking at it and start to realize the money they want to give out to the power plants is money they don't have.”