Civil Rights groups and the Congressional Black Caucus have begun an eleventh-hour lobbying effort to alter what they fear will be a damaging government legal brief before the Supreme Court.

An adverse ruling in the controversial "reverse discrimination" case, the Black Caucus has told President Carter, "would be a landmark setback for the civil rights of blacks" and would "jeopardize virtually all government programs which are designed to ameliorate the conditions of black people."

The remarks were included in a strongly worded position paper delivered to Carter, Vice President Mondale, Attorney General Griffin B. Bell and other high Justice Department officials in a series of meetings Wednesday.

Blacks Caucus leaders yesterday asked for a second meeting with the President and his chief legal advisers to re-emphasize their concerns over a proposed legal brief in a case involving Alan Bakke, a white student denied admission to a University of California medical school.

The proposed Justice Department brief takes a middle ground in a case that could produce one of the most important racial rulings since the school desegregation cases of the 1950s, according to adminstration officials. It states that race can be taken into consideration in university admissions to help minorities overcome past discrimination, but that quotas, such as one used in the Bakke case are unconstitutional because they deprive whites of their civil rights.

[Patrick Oster of the Chicago Sun Times reported that the brief asks the Supreme Court to apply the strictest legal test available when considering quotas, and allow them only when "a compelling state interest" requires their use.]

"It's a pro-Bakke [but] pro-affirmative action brief," said one high-ranking official. "It zigs and zags all over the place."

Bakke, an engineer, claims he was illegally passed over when he applied to the University of California Medical School at Davis, even though his grades and test scores were better than some minority students who were admitted. The school, as part of a special admission program, had set aside 16 places in its class of 100 for blacks, Chicanos and other minorities.

The case centers on whether the 16 slots were a fixed quota or a desirable goal. Members of the Black Caucus and many civil rights spokesmen maintain the slots do no represent a quota, and state that a pro-Bakke ruling would damage all preferential treatment programs designed to help blacks overcome past discrimination.

White House and Justice Department officials insisted the administration was revising the brief yesterday, and it was still considering various options. Carter was given the 88-page draft brief last Thursday.

Rep. Louis Stokes (D-hio), however, said he is afraid the President doesn't appreciate the political and social consequences of the brief.

"He can't afford the kind of attack that would come from the black community over an anti-black brief," he said. "The damage he'd do would be incalculable and impossible for him to overcome."

"This is not an issue to try to satisfy everyone," he said."The administration has to bite the bullet on this one and do the right thing."

Meanwhile, the NAACP, the National Urban League and several other groups were working with Black Caucus to mobilize the support.

"I've never seen the civil rights groups as united as they are over a Democratic administration taking a position like this," said Joseph Rauh Jr. of the Leadership Conference on Civil Rights. "How can they be pro-Bakke and pro-affirmative action at the same time?That's like saying you are for peace and war."