French Labor Minister Robert Boulin today posthumously accused his fellow Gaullists, especially Justice Minister Alain Peyrefitte of "obvious collusion" with those who were out to destroy him.

In a series of five letters mailed from a distant Paris suburb Monday, the day he committed suicide, Boulin said that the real estate operator he was involved with, "ambitious" investigating magistrate and "certain political circles from which my own political friends are, alas, not excluded" acted in concert to produce grave suspicions about the minister that led him to kill himself.

"A minister in office cannot be under suspicion, even less so a former minister of Gen. (Charles) de Gaulle," Boulin wrote. "I prefer death to being under suspicion, even though the truth is clear."

The Boulin letters created a major controversy in French politics, raising a number of basic questions about corruption, how politicians get ahead and regarding the separation of government powers. The implication that the current parliamentary majority is, in Boulin's phrase, "a basket of crabs," is bound to hurt the image of both the Giscardist and Gaullist parties.

In his letter, Boulin attacked current business ethics, revealing that he recently learned that his real estate agent had taken money from frightened frenchmen at the height of the Cold War to buy land for them in Brazil and them had "forgotten" to return the money when the scare passed.

Boulin, 59, a Gaullist who was seen as a possible successor to Prime Minister Raymond Barre, committed suicide following detailed press accounts of a questionable Riviera land deal in which he was allegedly involved.

In a separate note to the police, Boulin wrote, "I have decided to drown myself in a lake in the forest, of Rambouillet, where I enjoyed riding horseback." Boulin's body was found Tuesday morning in a shallow pond in the forest 30 miles southwest of Paris. An empty bottle of barbiturates was found nearby.

Before committing suicide Boulin also wrote letters to the French news agency, Agence France-Presse, to the newspaper Le Monde, to his wife Collette, and to his Gaullist colleague, Jacques Chaban-Delmas.

In the version addressed to and published by Agence France-Presse he accused a young Normandy judge of leaking details of the real estate case in an effort to seek personal publicity. In an politically charged attack on Peyrefitte he wrote that "this leaking of the secrets of the investigation failed to move a justice minister more concerned about his career than about the smooth functioning of justice."

Peyretitte, who is thought to nurture hopes for the prime minister's post, issued a long statement admitting that Boulin had come to him in June. Peyrefitte said that for him to have exercised " the least pressure on that judge would have constituted a serious fault that could legitimately have been held against the minister of justice."

The French magistrature historically has waged a constant struggle to maintain its independence, and political pressure on judges is common-place.

Besides, Peyrefitte said, Boulin did not ask him to exercise any pressure.

The labor minister, Peyrefitte said, only came to him to ask if he should be heard as a witness in the real estate scandal under investigation by Renaud van Ruymbeke, 27, the judge from Caen whose father was once a high-ranking aide to Boulin when the dead man was agriculture minister, Boulin expressed particular bitterness about the judge, calling him "ambitious, full of hatred for society and considering it to be self-evident that a minister is a liar." Boulin accused him of seeking "stardom" by getting" a minister.

The young judge refused all comment, and his colleagues in Normandy issued a communique stating their solidarity with him.

Boulin alleged that the judge let the real estate operator go free after serving a month in jail in exchange for his cooperation in implicating the labor minister. The land agent Henri Tournet, was "blackmailing" Boulin by trying to make it appear, untruthfully, that he knew beforehand that a building lot he bought from him on the French Riviera belonged to someone else, Boulin claimed.

Boulin said that upon bein freed from prison, Tournet went to the newspaper Le Monde and the satirical investigative weekly Canard Enchine, "whose basic motivation is maliciousness."

The dead minister said that a Le Monde reporter told him he had based a long article about the case last weekend on the revelations of the judge. But the reporter in question said that Boulin must have misunderstood him and that he had never met the judge and had only told the minister that there were publicly known documents in the case that looked bad for him.

The report of the suicide yesterday set off a furor about press responsibility center on charges against Boulin in the satirical weekly, Le Canard Enchaine and the daily Le Monde.

The accusations contained in Boulin's letters led National Assembly President Chaban-Delmas to say today that in speaking yesterday of "murder," he was not referring to the press but to whomever leaked the files in the case to the papers.

The financial newspaper, Les Echos today, however, denounced "muckrakers" out to destroy French society "in the name of morality" by exposing the scandals that politics "inevitably secrete." And in a statement at his weekly Cabinet meeting, President Valery Giscard d'Estaing also returned to the theme of a guilty press. Boulin, said Giscard, "was unable to resist the campaign of harassment he was subjected to. Public opinion should severly condemn any other similar campaigns.

Giscard was attacked earlier this month by the press for reportedly accepting diamonds in 1973 from then central African ruler Jean Bokassa.

Giscard said today that such campaigns, instead of attacking a person's exercise of public office, "aim to strike him in his self-respect, his family or his private life." These methods, Giscard said, ignore the idea that a man is innocent until proven guilty, and the person accused by the press is subjected to insinuation and guilt by association. The president called on Frenchmen of all political opinions to see to it that the political debate is once again conducted in "decency and dignity."

Reliable communist sources say that the way in which their party has insisted that the official party organ, L'Humanite, downplay the recent series of revelations by other left opposistion papers has stirred unrest in the middle reaches of the party.

"It had always seemed obvious," said a prominent young communist, "that we would help Giscard get elected. But I never thought we would be this open about it."