An intensive Army investigation has found no evidence to substantiate a television news report that a secret Army unit established an unauthorized Swiss bank account linked to participants in the Iran-contra affair, according to the Defense Department's chief spokesman.

CBS News reported in April that money from the account was used by Lt. Col. Oliver L. North and retired major general Richard V. Secord to lease a ship to carry arms to the Nicaraguan contras.

A senior Pentagon official confirmed the thrust of the story to reporters the next day and many newspapers, including The Washington Post, reported it on their front pages.

"The Army tells me it has investigated this exhaustively and it appears that there is . . . not any foundation for the basic thrust of the report," said Robert Sims, assistant secretary of defense for public affairs.

A Pentagon official, who asked not to be named, attributed the misleading information given to reporters in April to the Army's reliance on "the impressions" of one of the members of a secret unit code-named "Yellow Fruit."

The individual, William T. Golden, thought that he might have signed a signature card for a Swiss bank account. "We were going on belief, not facts," the official said.

Golden was a member of an Army front company called Business Security International, or Yellow Fruit, established in 1983 to provide security for other secret Army-CIA intelligence operations in Central America and the Middle East.

Sims said Wednesday that an Army lawyer accompanied Golden and an investigator for the Senate select committee probing the Iran-contra affair to Switzerland in an effort to check the CBS report.

Although they were not given complete access to bank records, the jurisdiction of independent counsel Lawrence E. Walsh, Sims said:

"The Army made as thorough a review as possible of the issue and after extensive analysis has found no evidence to support the assertion that Mr. Golden had a Swiss bank account in his name, or that Yellow Fruit had a Swiss bank account or that there was any connection between the Yellow Fruit unit and Lt. Col. North or Gen. Secord."

Sims added that the account number provided by CBS had "one digit too many and didn't have a suffix and didn't check out at all."

Jack Smith, the network's Washington bureau chief, said of the broadcast: "At this moment, we still think it's valid."

Spokesmen for Walsh and the Senate committee declined to comment on whether they are still pursuing allegations raised in the report.

Golden and a colleague in the unit accused its leaders of stealing funds, and Golden was a key witness in the federal criminal trial of Lt. Col. Dale C. Duncan, indicted on seven counts pertaining to justifying expense-account advances.

John M. Dowd, Duncan's attorney, said, "It's outrageous that the Army relied on Golden. He has no credibility."

Duncan's conviction on charges involving personal use of a $796 airplane ticket was dismissed by the 4th U.S. Circuit Court of Appeals a few days before the CBS report. He is serving a prison term after being court-martialed by the Army on similar charges.