SANTA BARBARA, Calif. — An environmental group sued the federal government on Wednesday for approving the use of hydraulic fracturing — fracking — on oil platforms off the Southern California coast.

The federal lawsuit by the Environmental Defense Center alleges the U.S. Department of the Interior and two of its subsidiary agencies approved 51 permits to drill from oil and gas platforms in the Santa Barbara Channel without properly conducting environmental studies or permitting public comment.

The permits, issued mainly within the past two years, allow the use of fracking or acid well stimulation at six platforms off the coasts of Santa Barbara and Ventura counties.

The procedures involve injecting large amounts of water, acid and other chemicals into the ground to fracture or dissolve rock.

"The use of these highly corrosive and hazardous industrial chemicals and acids poses significant risks to water and air quality and the many endangered species within the Santa Barbara Channel, including blue, fin and humpback whales, and the southern sea otter," the lawsuit contends.

The suit asks the court to bar the government from implementing the 51 authorization permits as well as all pending and future permits for the area until it meets requirements of the National Environmental Policy Act.

The Bureau of Ocean Energy Management had not seen the lawsuit and could not immediately comment, spokesman John Romero said.

The Bureau of Safety and Environmental Enforcement cannot comment on pending litigation, said Julia Hagan, a spokeswoman for the bureau's Pacific region.

After-hours messages left for representatives of the Department of the Interior were not immediately returned.

The region is home to Channel Islands National Marine Sanctuary and has more than 1,000 active wells.

Santa Barbara County has hosted oil derricks since the late 19th century. A 1969 offshore well blowout in the Santa Barbara Channel devastated area sea life, coated beaches in layers of oil up to six inches thick, and helped give rise to the modern environmental movement and to current national and state environmental legislation.

However, county voters last month rejected a ban on fracking and most other intensive drilling. Voters heeded warnings from the oil industry and business groups that the measure there would cost the county more than $300 million that the oil industry pumps into its economy annually.

Bans were approved by voters in San Benito and Mendocino counties, which have comparatively little oil.

California is the country's third-largest petroleum-producing state.