BALTIMORE -- Federal prosecutors have appealed last month's court decision that overturned the mail fraud and racketeering convictions of former governor Marvin Mandel and five political associates.

Concerned that their ability to convict corrupt government officials could be crippled if the decision stands, prosecutors asked the judge who made the decision to stay his order pending a decision by the 4th U.S. Circuit Court of Appeals in Richmond.

U.S. District Judge Frederic N. Smalkin vacated the convictions Nov. 12, citing a recent Supreme Court decision that limited prosecutors' ability to use the mail fraud statute in government corruption cases.

The judge ruled that the former governor and codefendants W. Dale Hess, Harry W. Rodgers III, William A. Rodgers, Irvin Kovens and Ernest N. Cory Jr. were convicted of using the mail to defraud citizens of their "intangible right" to good government, which the Supreme Court said in June is not a crime under federal law.

As of Friday, prosecutors still had not received approval from the U.S. Justice Department to pursue the appeal, but they filed notice within the required 30-day limit.

Martin S. Himeles Jr., an assistant U.S. attorney, said, "We expect to get approval."

The prosecution did not state its reasons for the appeal, but Breckinridge L. Willcox, the U.S. attorney for Maryland, has said he will raise a number of arguments, including that the 1987 Supreme Court decision should not be applied retroactively in this case.

Defense lawyers are expected to file a response this week to the government's request to stay Smalkin's ruling.

In their motion, prosecutors contended that the "primary practical effect" of the stay would be that the government would not have to return $160,000 in fines paid by Kovens, the Rodgers brothers and Hess, as ordered by Smalkin.

Mandel and the others have already served their prison terms. Mandel served 19 months of a three-year sentence.