A group of Filipino opposition leaders yesterday called on President Reagan to cancel his scheduled fall visit to the Philippines, charging the administration with "active collaboration" in the repressive policies of the government of Philippine President Ferdinand E. Marcos.

They also urged the Senate to reject a proposed extradition treaty with the Philippines, which they said would permit Marcos to extradite and imprison political opponents now in exile in the United States.

"It is our position that the extradition treaty as well as the other gestures that the Reagan administration has couched toward Marcos . . . has been . . . vital to the maintenance of the atmosphere of violence in the Philippines . . . . " said former Philippine foreign minister Raul S. Manglapus.

It was that atmosphere, Manglapus charged, which led to the assassination Aug. 20 of Philippine Sen. Benigno (Ninoy) Aquino Jr. as he stepped off a plane in Manila.

In Santa Barbara, White House spokesman Anson Franklin declined comment on the charges, but said the president's visit will go on as planned.

Manglapus, a longtime Marcos opponent and founder of the Washington-based Movement for a Free Philippines, asserted at a morning news conference with other speakers in the Capital Hilton that Marcos maintains an "invisible army" of secret agents in this country to harass his political enemies.

He said he personally had met a Filipino exile who reported being offered clemency for crimes in the Philippines if he "would only kill Manglapus."

Manglapus and other speakers said the Reagan administration is unique among the last three administrations in its embrace of the Marcos government.

"It's almost as if they get an aesthetic pleasure from association with figures of the political right," said Steve Cohen, a Georgetown University law professor who served as assistant secretary of state under President Carter.

Cohen said there appears to be no valid reason for the proposed extradition treaty, which he said had been opposed by the Carter, Ford and Nixon administrations.

"There are no stock swindlers or murderers hiding out in Manila," he said. "It is absolutely transparent that the motive of the Marcos regime for this treaty is to use the extradition process to harass, threaten and silence its opponents in the United States, and bring them back to the Philippines under trumped up charges . . . .

"It would be as if we signed an extradition treaty with the Soviet Union to help them extradite Soviet dissident writer Alexander Solzhenitsyn."