The nomination of James R. Taylor as chief of police in Prince George's County appeared in jeopardy last night after the leader of the county police union, angered by what he called a political blackmail attempt by the Hogan administration, said it would be impossible for his union to support the appointment.

Police union president Laney Hester charged that a top aide to County Executive Lawrence Hogan attempted to force him to suport Taylor at an afternoon meeting yesterday by threatening to hold up negotiations on the police union contract if Hester did not cooperate. Hester bitterly referred to the county executive as "Ayatollah Hogan."

Hogan, in response, called Hester's charges "incredible," and labeled the Fraternal Order of Police president an "Alabama racist" who had decided to oppose Taylor because "I refused to make a deal with him."

The vitriolic exchange of charges between Hester and Hogan signaled a political break that is likely to increase the difficulty Hogan will have persuading the County Council to confirm Taylor as chief.

The Fraternal Order of Police, which represents 840 officers, had been the only major county union to maintain good relations with Hogan during his first term in office. The police endorsed Hogan when he ran for county executive last year.

"The FOP made a serious political mistake when it endorsed Hogan over [Democratic opponent] Winnie Kelly," a bitter Hester said last night.

Hester charged that Kenneth V. Duncan, Hogan's chief administrative officer, called him to his office yesterday and sharply criticized him for failing to support Taylor for chief.

The union leader quoted Duncan as telling him that "if Taylor doesn't get the job, it is going to be total war between [the Hogan administration] and the FOP."

Hester said Duncan warned him that "if Taylor is not confirmed . . . your contract will never settle, or it will be the longest contract you ever negotiated."

Hester, who is regarded as an influential lobbyist of council members, also said that Duncan had told him that "it doesn't matter" what black groups "say or do" about Taylor. Taylor, now chief in Petersburg, Va., was selected by Hogan as the man who, in the county executive's opinion, could most improve the police department's image in Prince George's growing black community.

Finally, Hester said that if Taylor were not confirmed by the County Council, Duncan promised to "find the toughest guy we can [as a new chief] to go against you."

Duncan said last night that only part of Hester's account of the meeting was true.

"I told him that the county executive did not have a bad attitude about the [police] contract negotiations, but that if they are out there lobbying against Taylor, the attitude could change," Duncan said.

Duncan denied saying that the police contract would not be settled if the union opposed Taylor. He said that he had made "something like" the statement Hester attributed to him about black suport for Taylor, but added that he had "not meant to brush off or take lightly the black community."

"I simply made that statement in the the context of saying that I thought Hester could probably help influence four votes on the council," Duncan said. h

Hogan and Duncan responded to Hester by charging that he had attempted to trade the union's support of Taylor for a promise by Hogan that the county would drop its challenge of Hester's status as a full-time union official during the police contract negotiations, which began last month.

"This whole thing started when he tried to force me to capitulate to him and not try to put him back to work and I said no deal," Hogan said.

"Hogan is an absolute liar," Hester responded.

"I didn't call them to bargain -- they called me. I asked for no promises.

I wouldn't have talked to them if they hadn't called me up. I'll let the public decide which one of us is lying."

The split between Hogan and Hester, both well-known as street-fighters in the world of Prince George's politics, produced a storm of rhetoric last night as each man seemed to unleash tense feelings that had been building up for many days.

"This situation is similar to Iran," Hester remarked. "The Ayatollah Hogan is trying to hold our contract hostage because he's realized that his nominee is a turkey who's in trouble."

"I cannot believe that guy," Hogan said. "It's obvious that he has been trying to shoot down someone who's enlightened on race relations. Hester epitomizes what's wrong with the police department on race relations."

Taylor, 47, whose record of racial relations has become a central issue, will be formally considered by the council beginning with a public hearing on Dec. 3. The two black members of the council, Floyd Wilson Jr. and Deborah Marshall, have said that they will oppose the nomination if they and other black leaders in the county decide that Taylor's community relations record as chief in Petersburg and earlier in Newburgh, N. Y., was not really as strong as Hogan has portrayed it.

Since Taylor was nominated last week, reports have surfaced from Newburgh that he was disliked by several black leaders in that small New York city who claimed that he was insensitive to blacks. In addition, a black police officer in Newburgh sued Taylor, charging that he discriminated in police hiring.

While serving as Petersburg police chief, Taylor was nearly fired last year by the City Council, a majority of whose members are black. They sharply criticized Taylor for using lie detector tests in hiring, claiming that his hiring process was "racist."

Taylor and Hogan have denied all such charges, saying that Taylor has always worked well with minority groups. Hogan, in selecting Taylor, said he was the man who could best improve the police force's relationship with county blacks.