WASHINGTON (AP) - The Sierra Club has filed a lawsuit against the nation's interior secretary and the director of the National Park Service, alleging that the Bush administration quietly changed a rule so oil and gas producers could more easily drill under national parks from outside their boundaries.

The environmental group asked for an immediate injunction to reverse the rule change, which the Sierra Club said was done without public input. The suit also requests that the drilling be halted.

The lawsuit, filed in Washington, names former Colorado attorney general turned Interior Secretary Gale Norton, and National Park Service Director Fran Mainella, as defendants.

The Park Service denied the allegation.

"That is so untrue. There has been no change from the Bush administration, from the Clinton administration," said Carol McCoy, a Park Service spokeswoman based in Denver. "Nothing has been done outside the public process."

The Sierra Club alleged that a rule change affects 14 national parks that have privately owned minerals beneath them.

"The Bush administration bent over backward to help its friends in the oil and gas industry, even when the facts showed that its policy would harm national parks," said Brandt Mannchen, chairman of the Sierra Club's Lone Star chapter.

Oil and gas producers can drill at an angle to reach privately owned minerals from private land adjacent to a park.

Under a 1979 rule, the Park Service must study such drilling plans and their possible impacts to the park or adjacent land, Mannchen said. Also, the drilling company is required to submit environmental impact analyses.

But the Sierra Club alleges that since late 2001 the Park Service has been allowing directional drilling without such impact analyses. The environmental studies required of drilling companies also have been reduced, Mannchen said.

The Sierra Club alleged the change was in response to complaints about the process by Davis Brothers Oil Producers Inc., based in Houston. Davis Brothers wanted to drill along boundaries of the Big Thicket. A spokesman for the company could not be immediately reached.

Parks the group says could be affected are Gulf Islands National Seashore, Ala.; Big Cypress National Preserve, Fla.; Tallgrass Prairie National Preserve, Kan.; Big South Fork National River and Recreation Area, Ky.; Jean Lafitte National Historic Park and Preserve, La.; Aztec Ruins National Monument, N.M.; Cuyahoga Valley National Park, Ohio; Obed Wild and Scenic River, Tenn.; Gauley River National Recreation Area and New River Gorge National River, W.Va, and four Texas parks - Big Thicket National Preserve, Alibates Flint Quarries National Monument, Lake Meredith National Recreation Area and Padre Island National Seashore.

On the Net:

Sierra Club: http://www.sierraclub.org

Gale Norton biography: http://www.doi.gov/secretary/biography

U.S. Department of the Interior: http://www.doi.gov

National Park Service: http://www.nps.gov