Indignant lawmakers, reacting to tape-recorded plotting by deposed Philippine president Ferdinand Marcos, yesterday demanded stronger U.S. measures to restrain him, and a senior State Department official said Marcos might be placed under detention if he continues plotting from U.S. soil.

State Department legal adviser Abraham D. Sofaer, who warned Marcos Monday in Honolulu to stop seeking to disrupt the government of President Corazon Aquino and placed him under severe travel restrictions, said the United States would "escalate further" its attention to Marcos if he continues plotting.

Under intense questioning, Sofaer said he is "not confident" that Marcos will stop plotting, but that he could wind up in an Immigration and Naturalization Service detention center "if he takes steps that we believe warrant that outcome."

Sofaer's statements came near the conclusion of a marathon session of the House Foreign Affairs subcommittee on Asia and the Pacific, which heard tape recordings of Marcos' often-whispered plans to mount a military operation to regain power by overthrowing Aquino and taking her hostage.

The committee also heard lengthy testimony from Richard M. Hirschfeld and Robert Chastain, the two men who said they surreptitiously made the tapes in conversation with Marcos at his Honolulu home May 21.

{In an interview with Washington Post special correspondent Walter Wright in Honolulu, Marcos said he has asked his lawyers to question the authenticity of the tapes and declined further comment.}

In addition to previously reported details of an invasion plot involving 10,000 men to be profusely armed with weapons ordered from Hirschfeld and Chastain, the tapes and other testimony revealed that:

Marcos said he had given a $2 million down payment to other parties, whose identities are unknown, for weapons, presumably for use in the same sort of plot as that conveyed in the tape recordings.

Marcos claimed to have 1,000 tons of gold worth about $14 billion hidden in a secret cache. This is the equivalent of about half of the Philippine government's $27 billion foreign debt.

Marcos boasted of more than $500 million in Swiss bank accounts and provided Hirschfeld with a list of accounts, contradicting Marcos' public disclaimers of such hold- ings.

Former first lady Imelda Marcos was quoted by Hirschfeld as saying she was still friendly with Nancy Reagan and spoke to her early this year by telephone. A White House spokeswoman said Mrs. Reagan does not recall any conversation with Imelda Marcos since the well-publicized call in the spring of last year.

Hirschfeld and Chastain told a bizarre tale of hidden tape recorders and fake plans that caused Rep. Jim Leach of Iowa, the subcommittee's ranking Republican, to express his "deep-seated concerns regarding evidence gathered surreptitiously by private citizens, using false pretenses and false representations" with a principal motive appearing to be "profit generation."

Hirschfeld, a Charlottesville, Va., attorney who was the prime mover in the discussions with Marcos, said he and Chastain have had a contract with the Philippine government since early June that would provide them with a share of the proceeds if Manila is able to seize Marcos' hidden wealth due to information he provided.

Hirschfeld, who has represented prizefighter Muhammad Ali as well as colorful Saudi businessman Mohammed Fassi, was found in contempt of court last year for violating Securities and Exchange Commission antifraud provisions. No SEC actions are currently pending against him.

According to Hirschfeld and Chastain, they decided to tape Marcos using a bugged briefcase and a tiny pocket recorder after learning this January that Marcos was planning to use a loan being sought from Fassi to mount an invasion of the Philippines. Not to act on this information, they said, might have left them legally vulnerable and could have resulted in Philippine deaths.

Hirschfeld said he sought first to enlist the Justice Department to participate in an investigation. Hirschfeld's counsel, former assistant attorney general Jerris Leonard, said he gave a weapons shopping list drawn up by Marcos and other inside information to the Justice Department but, instead of cooperation, received a warning from the department, telling him, in effect, to "stick it in your ear."

Subcommittee Chairman Stephen J. Solarz (D-N.Y.), Rep. Chester G. Atkins (D-Mass.) and Leach called for the Justice Department to consider taking legal action against Marcos.