Pressure is building to reopen the investigation into the 1983 death of Philippine opposition leader Benigno Aquino as a senior prosecutor in the case charged today that deposed president Ferdinand Marcos rigged the acquittal of 25 military men and one civilian charged in the slaying.

Aquino was the husband of the country's new president, Corazon Aquino, who came to power last week with the help of a military revolt that forced Marcos to flee to the United States.

Defense Minister Juan Ponce Enrile, coleader of the military revolt, called today for a reopening of the case, saying it had "greatly defamed the Philippine military."

Aquino's killing in August 1983 was the starting point of the wave of organizing and protests that eventually put his wife in the president's office. The new president has said that she will seek the full truth about the slaying, but since assuming office, she has not treated it as a pressing issue. No decision on a retrial has been announced.

Manuel Herrera, head of a panel of prosecutors in last year's 10-month-long trial, said in a statement today that it was a "failure of justice" and suggested that a retrial would not constitute double jeopardy because the first one was not valid.

He said prosecutors and one of the three justices who tried the case at a special anticorruption court had attended a two-hour meeting at Marcos' Malacanang presidential palace, where "the outlining of the hows and whens of the trial" took place. Herrera compared the trial proceedings to a movie where he "already knew the ending."

Manila newspapers also quoted him today as saying that Marcos had pressured the court not to pursue the case because a conviction could lead to a "bloody incident." Herrera also said Marcos suggested that the trial be run in a staged manner, according to the newspapers. Marcos' legal adviser met with court officers to brief them on how to handle the case, Herrera reportedly said.

The court's chief prosecutor, Bernardo Fernandez, said on television today that there had been "pressure from some sources" during the trial.

An attorney for the family of Rolando Galman, the man the military accused of killing Aquino, has claimed that two of the acquitted defendants had confessed to involvement in the crime and had said that many more persons than the 26 indicted had been involved.

Attorney Lupino Lazaro was quoted by The Associated Press as saying the two defendants, whom he did not name, had implicated Marcos, his wife Imelda and four of his Cabinet ministers.

Ten to 15 of the defendants recently have been placed under a loose form of detention at Villamor Air Base in a Manila suburb, the Air Force commander, Brig. Gen. Ramon Farolan, said. This was being done, according to Farolan, so that they could be produced if required.

Aquino was shot on Aug. 21, 1983, at Manila International Aiport as he stepped off a jet that had brought him back from exile in the United States. The military blamed the killing on Galman, whom it called a Communist agent. Galman was gunned down by security agents.

However, an independent fact-finding board that Marcos was forced to appoint rejected that explanation and concluded that Aquino had been shot by one of his military escorts. Among those later indicted on conspiracy charges was Gen. Fabian Ver, armed forces chief of staff and a cousin and close confidant of Marcos.

The 26 were acquitted last December after a trial that opposition figures criticized for suppressing vital information and failing to explain how a single gunman could have penetrated airport security and known where to find Aquino.

In other developments today, President Aquino made more progress in obtaining resignations that she has said are necessary to reflect the change in government after Marcos' departure.

The nine members of the Commission on Elections, which Aquino accused of conspiring with Marcos to fix the results of the Feb. 7 presidential election, submitted their resignations today.

Only two of the 13 justices of the Supreme Court, who are in theory appointed for life, are still resisting her call. The judges of the special court that tried the Aquino case also quit today.

A special committee investigating the wealth of the Marcos family halted financial dealings in a number of accounts today and yesterday at three Philippine banks. One, the Security Bank and Trust Co., is headed by Rolando Gapud, a man whose name has appeared on a number of business transactions linked to Marcos and who is known as a longtime associate of Marcos in his business dealings.

Rep. Stephen J. Solarz (D-N.Y.), chairman of the House subcommittee on Asian and Pacific Affairs, called on Aquino today and delivered an invitation from House Speaker Thomas P. (Tip) O'Neill (D-Mass.) to address a joint session of Congress.

The official Philippine News Agency also reported that Marcos had planned to orchestrate a series of bombings, fires and assassinations after last month's election to provide an excuse to crack down on his opponents and prolong his rule.

The agency said the plan had been conceived by the now disbanded National Intelligence and Security Agency. The plot was overtaken by the fall of Marcos last week, the agency said.

In Washington, Japanese Deputy Foreign Minister Shinichi Yanai met with Michael H. Armacost, undersecretary of state for political affairs, and assured him that Japan intends to continue its role as a major aid donor to the Philippines, sources familiar with the talks said.

They said both governments agreed that specific aid plans cannot be made until there is a clearer idea of Manila's needs and economic priorities, Washington Post staff writer John M. Goshko reported.

[President Reagan's special envoy, Philip C. Habib, will arrive in Washington Friday and is expected to report quickly to the president and Secretary of State George P. Shultz his assessment of the Aquino government's needs.]