The Arlington County Board's Republican majority has decided to fire County Manager W. Vernon Ford, the board's two minority members said yesterday, accusing the GOP official of ousting Ford through "backroom politcs."

Board Members John Milliken, a Democrat, and Ellen M. Bozman, a Democrat-backed Independent, said that Ford, Arlington's manager since 1976, had been asked to resign Monday and was formally notified of the majority's position at a closed board meeting late Thursday night.

Board Chairman Stephen H. Detwiler and members Dorothy T. Grotos and Walter L. Frankland, all Republicans who have been quarreling with Ford for several years, would neither confirm nor deny the dismissal, saying no formal vote had been taken. "We did not demand anything," said Frankland, referring questions to Ford.

Under Virginia law, local officials may meet in private to discuss personnel matters, but formal votes to discharge an appointed official or accept his resignation must be made at a public session. The board's next public meeting is scheduled for Aug. 22.

Ford, 50, who has worked for the county 22 years, could not be reached for comment. Frankland said Ford was "on leave."

"He was a professional to the last second," Milliken said of Ford's reaction when he was summoned at the end of the 90-minute closed session Thursday. Bozman said she had a scheduling conflict and was not at the session, learning of the majority's decision yesterday morning from Milliken.

As county manager, Ford oversaw 2,4000 county employees and was responsible for the daily operation of the county government and preparation of the county budget which now totals $198.3 million. He serves as an advier to the five-member county board which can fire him from his $59,000 post at will.

Ford had assumed the county's top position when the board was controlled by Democrats, supported by the ostensibly nonpartisan Arlingtonians for a Better County. As soon as the Republicans took control of the board in 1979, they made it clear that they were unhappy with both Ford and School Superintendent Larr Cuban. Cuban resigned earlier this year, knowing that he would not be reappointed by the school board's Republican majority.

Grotos had been outspoken in her criticism of Ford in 1979 when she served as board chairman."We constantly find (Ford) in an adversary role rather than that of a helpful lieutenant," she charged at the time. "It is imperative that . . . there be complete cooperation between the county manager and the board. (Ford) should always defer to the will of the majority of the board on any given issue, or resign."

Miliken said that his colleagues gave no reason for their action during the Thursday session and set no time frame for choosing a successor. "The bottom line problem is the Republican majority has made a backroom decision to dismiss the county manager without consulting or even informing the entire county board," said Milliken.

"The decision has been made by them and I assume the mechanics of [picking a succesor] will be worked out by them, too," he added. "From the way they've operated, I don't expect we will be consulted any more than we were in the basic decision [to dismiss Ford]."

Despite the GOP's anger with Ford, Bozman said she was surprised by the action. "This is an unwarranted and unexplained dismissal," she said. When you treat top staff people and a competent professional administrator like Mr. Ford in this fashion, it really harms the community in the long and short run."

She and Milliken noted that Ford's dismissal would come at a bad time because of the intense development under way in the county and mounting budget problems resulting from federal aid cutbacks.

Bozman and Milliken noted that the full board had decided earlier this year on a routine evaluation of Ford's performance in office. The members, they said, met once in June and were to meet again with questions they wanted to raise with Ford, but the meeting never took place.

"If I had to speculate about their reasons," Milliken said, "I would say that Mr. Ford is not an enthusiast for their positions on economic development. But he has been very good in carrying out the directions of the board.

"I think (Detwiler) is frustrated that there is no majority on the board for his view of economic development and I think Mr. Ford is being used as a scapegoat for the majority's inability to provide a clear sense of direction for the community.

Both Grotos and Frankland complained about disclosure of matters discussed in the board's executive session. Grotos said: "I'm shocked they would call a press conference about what went on in executive session.I think it's unethical."