By Susan Cornwell

WASHINGTON (Reuters) - The investigative arm of Congress filed an unprecedented lawsuit against the White House on Friday, demanding to learn the role that energy companies including Enron Corp. played in developing the Bush administration's energy policy.

The General Accounting Office filed the suit in U.S. District Court in Washington, setting up a legal and constitutional battle with the Republican administration of President Bush.

The congressional agency is seeking records of an energy task force led by Vice President Dick Cheney that sought to draft a new national energy policy last year.

It is pursuing the case at the request of Democratic lawmakers who say environmentalists were mostly excluded from the closed meetings of the task force, which produced a policy calling for more oil and gas drilling, as well as a revival of nuclear power.

"We take this step reluctantly. Nevertheless, given GAO's responsibility to Congress and the American people, we have no other choice," the GAO said in a statement.

The White House argues that releasing the documents would damage the executive branch's ability to obtain candid outside advice. Officials said the administration was ready for courtroom combat.

"We have been ready to fight for this important principle since the GAO first indicated they were going to file suit last summer," White House spokesman Scott McClellan said on Friday. "And we look forward to the court reviewing this matter."

FIRST GAO LAWSUIT OVER ACCESS

It is the first time the 80-year-old GAO has taken the executive branch to court over access to documents; other such disputes have been settled out of court. Even former President Richard Nixon, who fought other court battles over executive privilege, handed over papers requested by the GAO.

The GAO asserts it has the right to the documents as part of congressional oversight of the executive branch. But the Bush White House says the GAO is overreaching its authority.

The White House acknowledges Cheney or members of the task force met six times last year with representatives of Enron, a major political contributor to Bush and other politicians that collapsed into bankruptcy in December.

But that is only part of the information GAO Comptroller General David Walker seeks.

He wants the names of everyone who met with any member of the task force and its staff to discuss energy policy, as well as the attendees at group meetings, names of task force staff, dates of meetings and the cost of the project.

Walker has, however, abandoned his original request for notes of the meetings. He had threatened to sue last September, but held off after the Sept. 11 attacks on Washington and New York.

BIG LEGAL GUNS

The original request for GAO action came last spring from Reps. Henry Waxman of California and John Dingell of Michigan, Democrats who suspected private-sector groups heavily influenced the White House energy plan.

"It's remarkable and sad that the administration has forced GAO to take this unprecedented action," Waxman said in a statement on Friday.

"Revealing names of lobbyists and campaign contributors may be unpleasant to the vice president, but as previous administrations have learned, avoiding embarrassment isn't a constitutional protection," Waxman added.

Cheney is himself a former head of an energy services company and Bush is a former oil man, but the White House denies its policy was overly influenced by energy companies.

The GAO works for Congress, evaluating federal programs, auditing federal expenditures and issuing legal opinions. It is expected to be independent and nonpartisan.

But its actions in this case have split Congress, with Republican leaders in both houses saying the GAO is not entitled to the information it seeks. However, a few Republicans have supported the GAO position.

Legal scholars are split on who might win in court. Some believe Bush has a constitutional right to withhold the information, while others say Cheney, in his role as the head of an inter-agency task force, is not protected by the normal constitutional powers of the vice president.

Bush has selected Solicitor General Theodore Olson, the government's top litigator, and Robert McCallum Jr., assistant attorney general in charge of the Justice Department's civil division, to defend the administration against the lawsuit.

Olson successfully argued for Bush before the Supreme Court in the battle with Al Gore over the disputed 2000 election.

The GAO is represented by Carter Phillips, appellate specialist and managing partner of Sidley Austin Brown & Wood.