President Ferdinand Marcos lashed out today at what he called "rumormongering and black propaganda" concerning him and his campaign for another term in office.

In a press conference, Marcos called on the news media to "correct itself" concerning the carrying of such reports and said, "I've never seen such a dirty campaign."

In the 90-minute session, Marcos:

*Denied that he plans to substitute his wife, Imelda, as his party's presidential candidate at the last minute.

*Denied that Dewey Dee, a financier who touched off a banking crisis when he fled Manila five years ago after running up enormous debts, had served as a front man to buy property abroad for him.

*Denounced as a fabrication a document that says U.S. military authorities concluded after World War II that a guerrilla unit Marcos says he commanded never existed as a fighting force against the Japanese.

Marcos said he has commissioned three investigative agencies in the United States to find out whether reports coming from there are part of an international conspiracy to discredit him. But one theory, he said, points to the domestic opposition as the source.

Opposition newspapers here have reported that the physically ailing Marcos may change his ticket at the last moment and substitute the name of his wife, Imelda. Under Philippine law, this could be done until noon on election day next Friday, meaning that votes cast for Marcos in the morning would go to his wife. Marcos said the report was "completely false."

Marcos also denied that financier Dee, a Filipino, acted as a front for him in the purchase of costly property abroad. According to reports in The Wall Street Journal, which have been reprinted in at least one Manila newspaper, Dee has told Canadian authorities that he did so. Dee is reported to have made the statements to support his petition for political asylum in Canada, claiming that he is under danger from Marcos.

"Hidden wealth" has emerged as a major campaign issue, with Marcos' opponents contending that he has invested huge sums of improperly acquired money abroad and has contributed to the Philippines' economic crisis. Marcos has denied the allegations.

Today, Marcos said he might have met Dee but "I don't know him."

Marcos condemned U.S. congressional hearings into allegations that he has major properties in the United States. He said the hearings' sponsor, Rep. Stephen J. Solarz (D-N.Y.), wishes to influence the outcome of the voting here.

Marcos also assailed critics who say his record as a hero during World War II is largely false.

Last month, press reports said that after the war, U.S. military authorities who investigated an application from Marcos to recognize a guerrilla unit he says he commanded concluded that the unit had not existed as a fighting force.

Today, Marcos denied that he had ever filed such an application for unit recognition and said the one presented against him in the press reports was "a fabrication."

He said the unit was so well known that "even the emperor of Japan devoted some 11 pages of his diary" to it. However, Japanese sources said that Emperor Hirohito has never published a diary.

The government announced Saturday that Marcos had ordered a 10 percent pay increase for 825,947 government workers, police and armed forces personnel, United Press International reported.

Elsewhere in the campaign today, opposition presidential candidate Corazon Aquino held rallies near Manila and spoke on a radio call-in show.

In the province of Bataan outside Manila, she said she would not allow the opening of a nuclear power plant there that is nearing completion, citing safety and environmental concerns.

Imelda Marcos, meanwhile, carried the campaign to Tacloban City, where she said Aquino "is worse than a Communist because she is allowing herself to be used by the Communists."

Imelda Marcos also denied the "hidden wealth" allegation. "My hidden wealth is in my heart," she said.