The U.S. Court of Appeals yesterday upheld the conviction of former representative George Hansen (R-Idaho), who was found guilty last year of four counts of filing false financial disclosure statements with Congress, including three concealing his family's dealings with Texas billionaire Nelson Bunker Hunt.

The three-judge appellate panel unanimously agreed that violations of the 1978 Ethics in Government Act were covered by criminal sanctions, rejecting the seven-term congressman's contention that he should have only been subject to a civil penalty.

Hansen, who was defeated for reelection last fall by 170 votes out 202,000 cast, was convicted under a provision of a separate federal law that prohibits the willful filing of false statements with the federal government. He was fined $40,000 and sentenced to a 5- to 15-month prison term.

Sen. Orrin G. Hatch (R-Utah), House Majority Leader James C. Wright Jr. (D-Tex.) and 121 other House members supported Hansen's argument that Congress did not intend to criminally punish violators of the ethics act.

But Judge Antonin Scalia, writing for Judges Ruth Bader Ginsburg and Carl McGowan, said that if Congress had wished to exclude criminal penalties for ethics law violators, "it normally would have said so; we will not readily conclude that it did so by implication.

"Hansen has not only not been surprised by a novel or unexpected interpretation of the law," the court said, "but was in fact warned of its application with a specificity that a prospective lawbreaker rarely enjoys. The forms that Hansen signed all contained a warning, immediately above or below the signature line, that 'any individual who knowingly or willfully falsifies, or who knowingly and willfully fails to file this report may be subject to civil and criminal sanctions.' "

Hansen, who is free while appealing his conviction and working as a lobbyist and consultant here, could not be reached for comment. One of his attorneys, Frank A.S. Campbell, said that Hansen would either ask the full appellate court to overturn the three judges' decision or appeal the ruling to the Supreme Court.

Hansen, the first congressman prosecuted under the ethics act, was convicted of failing to report four major financial transactions: loans totaling $135,000 to him in 1981 from three southern Virginia men; a $61,503 loan by Hunt in 1980 to Hansen's wife, Connie; an $87,475 profit by the Hansens on purchase and sale of 125 silver contracts during a two-day period in 1979, andA $50,000 loan by a Dallas bank to Connie Hansen, a note guaranteed by Hunt.

Hansen contended at his trial that he did not have to report the Hunt transactions because he and his wife had a legal arrangement in which Connie Hansen had separate assets and liabilities, and that two attorneys had advised him he did not have to report the transactions on the disclosure forms. He claimed that the loans from the Virginians were intended for a tax-reform group he headed and need not have been reported.