BP filling station operators in the western United States sued BP PLC seeking $200 million in damages over allegations the company’s sales and inventory software they are forced to use is “an unmitigated disaster.”

A group of BP, Arco, and AM/PM Mini Market franchisees, based in California, Oregon, and Washington, said in a complaint filed Wednesday in Los Angeles that the software program they were forced to buy for as much as $35,000 overcharges some customers, doesn’t charge others, and periodically crashes.

The franchisees said the software program, in which BP had invested, is but one instance in which they had a contract forced upon them.

They also can buy only from suppliers that pay BP a fee, and BP’s refusal to approve alternative vendors suggested by the franchises has cost them tens or hundreds of thousands of dollars in damages, according to the complaint.

First Published May 5, 2011, 4:32 a.m.