William M. Kunsbler charged Saturday night that the Federal government is conspiring to "destroy the antiwar movement" by prosecuting the Rev. Philip Berrigan and five others in Harrisburg, Pa.

Kunstler also accused FBI Director J. Edgar Hoover of fabricating the conspiracy charges both to destroy the radical left and to increase the strength of the FBI.

Kunstler, who was chief defense counsel in the Chicago 8 and Catonsville 9 conspiracy trials-and faces a four-year sentence for a contempt of court conviction stemming from the Chicago trial-spoke to 700 persons in Lowell Lecture Hall Saturday.

He was invited by the Harvard-Rad-cliffe Catholic Center as the first speaker in their three-day "Response to Repression."

Kunstler attacked the government's choice of Harrisburg as the site of the grand jury investigation, and thus of the conspiracy trial. At least three other cities could have been selected, he said, since the alleged conspiracy existed in at least four East Coast cities: Harrisburg;, Lewisburg, Pa., Danbury, Conn.; and Seeburg, N.J.

Kunstler charged that the government chose Harrisburg-predominantly Protestant-because of its citizens' pro-war attitudes and their allegedly anti-Catholic bias.

'Reichstag Fire'

Kunstler compared the Harrisburg conspiracy trial to the burning of the Reichstag in 1933. Just as the Nazis were determined to discredit their main opposition, the Communist Party, he said, the Federal government is trying to convince the American public that a widespread threat of terrorism exists within the U.S.

Paul Couming, a draft resister who faces a possible 15-year sentence for draft law violations, also spoke at the meeting.

Couming is one of 74 people indicted in the Boston area within the last four months by the Federal government for Selective Service violations. He faces possible sentences of five years each for non-possession of his classification card, and for leaving the alternative service to which he had been assigned as a conscientious objector.

Hoover made his allegations against the Berrigans before a closed sessionof a Senate Appropriations subcommittee on November 27, 1970. He was requesting $14 million to train 1000 additional FBI agents.

The next day the Berrigans issued a statement through their lawyers demanding that Hoover either "prosecuteus or publicly retract the charges he has made."

Both Berrigans are currently serving terms in a Federal prison for destroying Selective Service records in Baltimore, Md. in 1968.

The six indicted-Berrigan. Eqbal Ahmad. Sr. Elizabeth McAlister, Rev. Neil McLaughlin. Anthony Scoblick, and the Rev. Joseph Wenderoth-face possible life imprisonment if convicted of plotting to kidnap Henry Kissinger and blow up government property.

The grand jury termed 7 others, including Daniel Berrigan, "co-conspirators," but failed to indict them.

Couming's trial begins today at 10 a.m. in the Boston Federal District Court, Post Office Square.