Former representative Daniel J. Flood (D-Pa.) is expected to plead guilty in federal court today to a misdemeanor conspiracy charge as part of an agreement with government prosecutors that will apparently resolve more serious conspiracy, bribery and perjury charges against him.

Flood, 76, once one of the most powerful and flamboyant members of Congress, is expected to appear this morning before U.S. District Court Judge Oliver Gasch.

The exact nature of the charge involved in Flood's expected guilty plea was nuclear last night. It was learned that a detailed plea agreement was prepared to be read in court today.

Gasch had ruled earlier this month that Flood, who has been in poor health, was mentally competent to stand trial a second time on criminal charges that he took more than $50,000 in bribes from businessmen in exchange for his influence as chairman of a House Appropriations subcommittee.

Flood's first trial ended with a hung jury a year ago.

During lengthy hearings in January, Flood's lawyers had argued that their client's mental capacities had deteriorated to the point where he was unable to either understand the charges against him or assist in preparation of a defense. Gasch, however, agreed with a court-appointed psychiatrist who test-agreed with a court-appointed psychiatrist who testified that it would be "difficult but not impossible."

Flood himself took the witness stand for several hours during those hearings and strongly denied the government's allegations that he had accepted any payments or violated any laws. At one point, Gasch remarked that Flood would be acquitted if he defended himself at trial with the same vigor he showed at the competency hearing. Flood resigned from Congress Jan. 31.

A second trial was scheduled to begin April 8. A guilty plea, however, would presumably dispose of any further prosecution of the case.

Gasch declared a mistrial in the government's first case against Flood in February 1979 afther jurors were unable to reach a verdict after 12 hours of deliberation after a 15-day trial.

Flood had been charged with 11 criminal violations in connected with various unrelated payments he allegedly received from people who sought his help in obtaining government favors. The resecution alleged that the money was paid by, among others, a foundation director, a housing developer, a New York rabbi and a trade school operator.

Sources said at the time that a single juror kept the panel from finding Flood guilty on all but two of the charges.

One juror quoted the lone holdout as saying, "I know he's guilty on some charges, but I'll never vote to send an old man to jail."