BOSTON, JUNE 13 -- The Massachusetts Democratic Party today filed suit against a White House official for allegedly planning with a police union chief to disrupt the Democrats' convention earlier this month.

Party officials charged that Ronald C. Kaufman, a deputy assistant to the president for personnel, "gave encouragement and assistance" to the police union, which threw up a picket line outside the convention hall in Springfield, Mass., on June 2 and disrupted the Democratic gathering for five hours.

They asked for unspecified damages, contending that their civil rights were violated, particularly their right to free association.

Kaufman, a Republican National Committee member from Massachusetts and the Northeast political director for Bush's 1988 presidential campaign, has denied involvement in the picketing. Robert Jacobson, president of the police union, said today he and Kaufman never discussed it.

Kaufman, who was instrumental in the police union's endorsement of Bush during the 1988 campaign, met with Jacobson in May in Washington, but both men say they did not talk about disrupting the convention. According to the union chief, the picketing grew out of a bitter local labor dispute and was prompted by the rank and file.

Kaufman did not return several calls to his office. In a statement issued by his Boston attorney, R. Robert Popeo, he said the Democrats "were unable to recite even one specific act by me. . . . That is because no such act exists."

Also named in the suit, filed in Hampden County Superior Court, was Stephen DeAngelis, who was field director for the campaign of the GOP candidate for state treasurer, Joe Malone. DeAngelis quit Tuesday to defend himself against the Democrats' charges.

A key piece of evidence in the case is a statement provided by another former Malone staffer, Sean Keegan, 22, who gave a taped statement to the Democrats' attorney, Max Stern. In his statement, Keegan said DeAngelis told him on June 2 that DeAngelis had been "in Springfield, screwing up the convention for five hours with Ron Kaufman."

Keegan said DeAngelis repeated his claims later and quoted him as saying, "We used Kaufman's influence, we used his clout to persuade the union president, the police union president, to hold this strike. . . . "

Keegan was fired by DeAngelis from the Malone campaign last week, and Republicans here depict him as a disgruntled young man who may be seeking revenge against his former boss.

But other eyewitnesses have told Democratic Party officials that they saw DeAngelis standing near the picket line with a portable telephone, and Kaufman has acknowledged that DeAngelis called the hotel room where Kaufman was staying during the picketing.

DeAngelis's attorney, Morris Goldings, said today that his client had no role in arranging the picket line and that the suit was a political "diversion" that did not belong in court.

At the White House, senior officials showed little concern over the charges, attributing them to Massachusetts politics and noting that there has been little interest outside Boston. "Everyone believes Ron and no one is worried about it," one White House official said.