An increasingly bitter battle over the tenure of Bill Brock as chairman of the Republican National Committee is going to be dumped into Ronald Reagan's lap at a meeting in Los Angeles Friday.

The question -- which seemingly was settled last month in favor of retaining the former Tennessee senator for the duration of the campaign -- has blown up in the last few days into a major test of the ideological direction of Reagan's presidential campaign and the power relations in his high command.

Sen. Paul Laxalt (R-Nev.), who has been leading the effort by conservative activists to dump Brock, said yesterday that "Ron's going to have to make a decision one way or the other in the next few days. It's his decision."

Laxalt said he hoped the issue would be decided in the meeting between Brock and Reagan, with the help of "a comprehensive report" on the Republican National Committee. The report critical of Brock, was written by Jerry Carmen, Reagan's former New Hampshire chairman, who has been mentioned as a possible Brock replacement.

"The Reagan campaign is no longer a country store operation, and it needs a committee responsive to the nominee," Laxalt said. "Bill Brock has done a good job but Ronald Reagan like other nominees, is entitled to the chairman of his choice."

Brock, who is going to California Friday for an ironically named "unity dinner" with Reagan and several defeated GOP presidential aspirants, was reported by friends to be "mad as hell" and "eager for a showdown."

Brock has rejected a face-saving suggestion from some high-ranking Reagan aides that he step down and become "chief spokesman" or "chief surrogate" of the Reagan campaign.

He told The Washington Post last night that "I am operating on the assumption that I have the governor's [Reagan's] support and that of his campaign manager," William J. Casey.

But Casey said last night, "I'm not sure we're going to work out a satisfactory arrangement or not. I have been hoping that Brock will make arrangements with us that will make us want to keep him. We thought it was worked out before, but it hasn't been."

Allies of Brock -- sensing that the move to dump him has gained fresh strength this week -- began mobilizing Republican governors, members of Congress and national committee members on his behalf.

The implications of the situation for Reagan's campaign were viewed so seriously that the six top GOP congressional leaders met last night at the invitation of Sen. John G. Tower (R-Tex.) to discuss the situation.

According to some participants the group was unanimous in recommending Brock's retention. But one of those present said that if the decision went the other way, the group felt it was very important that "it should not appear that Reagan fired him."

"Brock's reputation in the party and the country," this source said, "is such that it would hurt Reagan a lot more than it would hurt Brock."

Since becoming chairman in 1977, Brock has expanded the staff and budget of the national committee significantly. But he clashed with Laxalt and other conservatives in 1977 when he refused to help finance a cross-country airplane tour to mobilize support against the Panama Canal treaties. His neutrality in the 1980 nomination contest also was viewed with suspicion by some conservatives.

Laxalt said yesterday that he favored Reagan "getting his own people in there" at the national committee. But when Brock met with Reagan and Casey in California last month, he left with the impression that they wanted him to remain as chairman through the campaign period.

After Brock told that to members of the national committee and announced that he would seek reelection, Reagan aides circulated word that his continued tenure was dependent on his willingness to let the Reagan organization designate the national committee staff members who would run the party's campaign effort on a day-by-day basis.

Some of them said that Brock was balking at removing co-chairman Mary Crisp and political director Ben Cotton to clear the way for the Reagan appointees. They also said there was friction over Brock's hiring of several aides dumped from the Reagan campaign when John P. Sears was fired as campaign manager last February.

Brock, however, contended that the hiring of the former Reagan aides had been cleared with Reagan and denied that he was being recalcitrant in accepting suggestions from the Reagan camp on new staff appointees.

Specifically, he said that he was "very willing to work with Drew Lewis," the head of Reagan's Pennsylvania campaign and reportedly the choice as de facto national political director for the fall.

But Lewis' name was mentioned by some Reagan aides as a likely choice to replace Brock if the party chairman was dumped.

Reagan's position on the question was unclear yesterday. It has long been unknown that Laxalt, the part-time chairman of the Reagan campaign, was strongly in favor of replacing Brock. Several sources said that Reagan's top California aides, who previously had argued that a changeover was not worth the controversy it would cause, were swinging to the view that Reagan should have his own man as chairman.

The apparents trend was viewed by some non-Reagan Republican officials as evidence that Casey -- a New Yorker brought in to replace Sears last winter -- was, like his predecessor, being undercut by Laxalt and aides from Reagan's days as governor of California.

Congressional leaders and other arguing for retaining Brock contend that the chairman has a near-universal reputation for competent leadership and that replacing him would convey a signal that Reagan places personal loyalty above a pragmatic desire to involve all elements of the party in his campaign.

They also reportedly were disturbed by reports that the dump-Brock leaders were primarily concerned about controlling the party mechanism if Reagan should be defeated.

They expressed concern to Reagan lieutenants that replacing Brock might suggest that ideology would come before electoral considerations in the more important choice of Reagan's running mate.