Rep. Charles C. Diggs (D-Mich.), sentenced in November to a maximum of three years' imprisonment for illegally diverting more than $70,000 of his personal use, has reduced his personal debt since then by more than $100,000, his lawyers reported yesterday.

In a legal brief asking U.S. District Court Judge Oliver Gasch for a reduction of the 13-term congressman's prison sentence, the lawyers said that Diggs' financial obligations have been pared from $178,068 to $67,252.One of the lawyers, David Povich, said Diggs paid off most of the debt through the sale of his $235,000 Capitol Hill home to an Ohio congressman.

Among his remaining debts are $29,523 owed to the Internal Revenue Service for taxes on his father's estate, a disputed $28,955 obligation owed primarily to a D.C. creditor that is being negotiated and $8,774 in miscellaneous liabilities, according to Povich and the legal brief.

Gasch invited the request for the sentence reduction at the time he imposed the three-year prison term. But it was not immediately clear yesterday whether Gasch still has jurisdiction over the case, since Diggs has appealed the jury verdict to the U.S. Court of Appeals.