A racially tinged dispute between a group of black D.C. police officers and the leadership of the Fraternal Order of Police threatens to blunt the effect of the union's endorsement of D.C. Council member Carol Schwartz (R-At Large) in the race for mayor.

Police Sgt. Lowell Duckett, who told reporters Thursday that FOP labor leader Gary Hankins engineered the endorsement without consulting black police officers who support Mayor Marion Barry, said Friday his group is polling the police force on the question and may seek the removal of Hankins, who is white. Duckett earlier described Hankins' criticism of Barry as "racially motivated."

Hankins, acknowledging that the protest group has been active, charged that Duckett has approached black officers "trying to make this an acid test of whether you are black or an Uncle Tom."

The clash, centering on the FOP's decision to endorse a white challenger against a black incumbent, threatens to aggravate racial tensions in the union that can be traced to the FOP's ouster five years ago of the International Brotherhood of Police Officers (IBPO), the former bargaining agent for officers and sergeants.

In addition, Duckett's group, which is supported by the Afro-American Police Officers Association, has raised questions about the FOP's procedure for endorsing candidates.

Ron Hampton, president of the 300-member Afro-American Police Officers Association, said the FOP did not follow the precedent set four years ago when it held a well-attended candidates forum, which led to a heated debate on the mayoral candidates and a decision to endorse no one in that race.

Hankins recalled that the FOP did not make a mayoral endorsement four years ago because there was no consensus. This year, he said, the union interviewed a number of mayoral candidates -- but not Barry.

The FOP has clashed with the mayor on a police pay raise, the city's residency requirement for police officers and what Hankins terms political interference by the mayor in police operations.

"In the case of the mayor's race, we were interested in everybody but the mayor," he said. "We interviewed the candidates that would be acceptable to the rank and file. The mayor is not at all popular among the rank and file."

Hankins, asserting there was no racial element in the decision to back Schwartz, pointed to the group's provisional decision in June to endorse D.C. Council member John A. Wilson (D-Ward 2), who is black. The endorsement was withdrawn when Wilson declined to enter the race for mayor, Hankins said.

The endorsement of Schwartz, recommended by the FOP's 20-member executive committee, was ratified unanimously by the general membership at a meeting July 16, Hankins said, adding that 75 to 100 of the union's 3,270 members attended the meeting.

Hampton charged, however, that the endorsement proceeding was not adequately publicized.

"The majority of the folks the union represents didn't know anything about the doggone thing," he said. "If you are going to make a decision as important as that, then . . . it should be incumbent on you to make it known so that people can be aware."

Duckett, in leveling the charge that Hankins and other FOP leaders are out of step with the rank and file, noted that Hankins and FOP President Thomas J. Tague live outside the city. "We will not tolerate our political system to be corrupted or influenced by those who live outside our city," he said.

Hankins and Tague, who is also white, are strong opponents of the city's requirement that police officers live in the city, contending that many cannot afford housing here. Schwartz has called for flexibility in the requirement. Duckett, meanwhile, said he supports the residency requirement, which took effect in 1980.

Police officers and sergeants who live outside the city and were hired before 1980 are not required to move into the District. About 825 of the FOP's members reside in the city, according to Hankins.

The friction in the union dates to the 1981 campaign by the FOP to replace the IBPO. The brotherhood, with a large black membership, had been a strong supporter of Barry, while the FOP had a history as a predominantly white social organization and has clashed with Barry.

Disenchantment with the IBPO's representation of its membership in contract negotiations bled the organization of support. And, with the FOP moving to embrace black membership, the rank and file voted out the IBPO in December 1981.

Estimates of black membership in the FOP now range between 50 percent and 63 percent, a substantial increase since 1981. But, said Duckett, a new challenge to the FOP may be afoot.

"We are going to accomplish the same thing we did with the IBPO," he said. "If our union is going amok . . . then we are going to wind up with another union."