A coalition of minority-owned firms has accused the California High-Speed Rail Authority of systematically excluding them from bidding for work on the $43 billion project.

A federal civil-rights complaint filed Wednesday by the Associated Professionals and Contractors asks the U.S. Department of Transportation to withhold federal money for the rail project until it investigates the state agency's contracting practices.

Businesses operated by minority owners "are largely being shut out of contracting opportunities," states the complaint filed by attorney Oren Sellstrom of the Lawyers's Committee for Civil Rights, representing the business coalition.

Of 134 prime and subcontractors in the 10 largest management and design contracts awarded so far for the rail project, Sellstrom said, only about a dozen are minority-owned.

"Federal intervention is necessary to stop this inequity and to ensure that [the authority] does not continue to funnel billions of dollars ... into an exclusionary contracting system," Sellstrom said.

Projects receiving federal funds must provide fair opportunities to minority firms to bid for work. About $3 billion has been set aside by the federal government -- but not yet delivered -- for California's high-speed rail program. The rail authority is counting on $15 billion to $17 billion in federal funds over the next decade to build the 800-mile system.

On Wednesday, the rail authority defended its compliance with the law.

"Our contracts are awarded in a very public and transparent manner by our board, in public meetings," said Valerie Martinez, the authority's small-business liaison. "We are committed to further ensuring that every Californian and every community has an equal opportunity to access the economic benefits of the project."

Spokeswoman Rachel Wall said the authority is setting up a small-business advisory committee and making it easier to connect would-be vendors with prime contractors. Those steps are expected to be complete before the agency awards $4.3 billion in engineering, design and construction contracts for the first segment of construction in the central San Joaquin Valley.