The Vatican strongly defended its former envoy to Argentina today against what it called slanderous accusations that he was involved in human rights violations during what became known as that country's "dirty war."

Cardinal Pio Laghi, who now heads the Vatican's Congregation for Catholic Education, also denied the charges. They were leveled by the Mothers of Plaza de Mayo, a group that has campaigned on behalf of victims of Argentina's former military dictatorship.

Representatives of the group came to Rome this week and announced at a news conference that they had asked the Italian Justice Ministry to investigate Laghi for alleged complicity in torture, murder and kidnapping while he was the Vatican's ambassador to Argentina from 1974 to 1980.

The group said it wants Pope John Paul II to lift Laghi's diplomatic immunity so he can be prosecuted.

Critics have long charged that the Roman Catholic Church in Argentina failed to use its voice and stature to oppose excesses of the military regime that ruled from 1976 to 1983. Unlike in some other parts of Latin America, where Catholic bishops and priests espoused left-leaning liberation theology, the church in Argentina was a conservative institution, opposed to leftist influences that the country's military rulers were trying to eliminate.

"We understand and share the pain of the Mothers of Plaza de Mayo, of every other group and individual, but we maintain that making a moral attack against the nonexistent responsibility of the then-apostolic nuncio is an act against justice, honesty and historic truth," the Vatican's daily newspaper, L'Osservatore Romano, said in a commentary in today's edition. Ambassadors from the Vatican carry the title of apostolic nuncio.

"In expressing our full solidarity with Cardinal Pio Laghi, we firmly reject these slanderous accusations," the newspaper said. "In this way, they want only to cast a shameful shadow on the church and on the apostolic nuncio, who has the right above all else to be respected as a man and as a priest."

The Vatican commentary was published alongside texts of Laghi's denial and a statement of solidarity by the executive committee of the Argentine bishops' conference. Laghi said the accusations were "defamatory and devoid of content and foundation."

"My work as apostolic nuncio in Argentina from July 1, 1974, to the end of December 1980 is well documented by both the bishops of Argentina and {the Vatican's} secretary of state," he said in the statement, which also was read on Vatican Radio and released by the Vatican's press office. "The documents are in their hands."

In his current post, Laghi oversees Catholic school teaching around the world. He also was the Vatican's ambassador to the United States from 1984 to 1990. CAPTION: CARDINAL PIO LAGHI