Virginia Attorney General Gerald L. Baliles has filed a lawsuit in Arlington in an effort to block a transit union from requiring some Metro workers in Virginia to belong to the union.

The suit was brought at the request of Virginia legislators who have argued that under the state's "right to work" law the workers should not have to join a union as a condition of their employment.

Republican Wyatt B. Durrette, Baliles' opponent for governor this fall, has charged that Baliles has been reluctant to support the law for fear of losing union support. Labor spokesmen have countered that Metro was created by an interstate authority run by Virginia, Maryland and the District and thus is not subject to Virginia labor laws.

Deputy State Attorney General William G. Broaddus said yesterday that the suit, filed in Arlington Circuit Court, would not affect Virginia residents who work for Metro in Washington or Maryland.

Named as defendants in the suit were the Washington Metropolitan Area Transit Authority, which runs the regional bus and subway system, and Local 689 of the Amalgamated Transit Union AFL-CIO, which has about 5,800 active members regionally, including nearly 1,000 who work in Virginia.

James M. Thomas Jr., president of Local 689, said the suit was "ill-advised" and will cost Baliles, the Democratic nominee for governor, union support. "If I've got anything to do with it, it will," Thomas said.

Longstanding labor contracts between Metro and its unions allow the unions to require membership as a condition of employment. Local 689 represents a variety of clerical, construction and maintenance employes, who pay $20.80 a month each in union dues.

Metro spokeswoman Marilyn Dicus said she did not expect the agency to comment on the suit yesterday.

The suit comes on the heels of an unsuccessful attempt last year by Virgina to persuade Maryland and the District to amend the regional transit compact to reflect Virginia's "right to work" laws.

"Our position is that when Virginia entered into the original Metro contract, the state did not waive its policy," said John S. Battle, whose Richmond law firm was hired by Baliles to handle the suit.

After failing to get an amendment to the Metro compact, the legislature passed a resolution asking Baliles to file suit, action some legislators wanted Baliles to take two years ago. Baliles said at the time he believed it was preferable to seek agreement with Maryland and the District to change the original charter before suing.

The issue arose initially, according to the union's Thomas and others, when a former member of Local 689 sought to withdraw from the union and keep his job. The man went to the Springfield-based National Right to Work Committee, which in turn contacted supporters in the legislature.

State Del. Warren G. Stambaugh (D-Arlington), a member of the House Committee on Interstate Cooperation, said he did not believe the suit "has a prayer in the world. It's clearly challenging an interstate compact."

Stambaugh and state Sen. Edward M. Holland (D-Arlington) said they did not expect the suit would hurt Baliles politically.