Government investigators, acting on instructions of FBI Director William H. Webster, conducted background checks on four congressmen later convicted of accepting influence money and found "derogatory information" on all four, a federal prosecutor said Tuesday.

"On every congressman there was an allegation of a criminal nature," chief prosecutor Thomas Puccio said at a due-process hearing for the four and three other defendants convicted in three separate Abscam trials in Brooklyn.

Without providing any details, Puccio attempted to introduce four FBI memorandums that he said would show that the FBI had "derogatory information" available on the four before they appeared at payoff meetings with undercover FBI operatives.

U.S. District Court Judge George C. Pratt, who is conducting the hearing, refused to allow the introduction of the memos, saying the material "would seem to have a highly prejudical impact" on the four defendants: Rep. Raymond Lederer (D-Pa.) and former representatives John Murphy (D-N.Y.), Frank Thompson (D-N.J.) and Michael Myers (D-Pa.).

"You are opening a can of worms I don't want to have to dig through if I don't have to," Pratt told Puccio.

In three instances, the information, which Puccio said came from confidential unformers, did not result in criminal charges. The fourth case involved a "no contest" plea by Myers to charges of disorderly conduct resulting from a fracas in which Myers was accused of attacking a hotel security guard and a female cashier.

Michael Wilson, supervising agent of the FBI's Criminal Investigations Division, testified that the background checks had been included in guidelines issued by Webster in the spring of 1979, before the payoff meetings.