Rep. Dawson Mathis (D-Ga.) is being investigated by a federal grand for alleged violations involving the handli of his Albany, Ga., office payroll.

According to a spokesman for Mathis, three of his Georgia employees and two former employees were subpoenaed to testify before a Macon, Ga., grand jury last week.

Mathis denied ay wrongdoing and issued a statement accusing his former Georgia district coordinator, Norman Gay, of "attempting to use the legal processes of our courts to carry out his campaign to discredit and destroy me and my career."

Gay was fired by Mathis last June after admitting that he placed a hidden microphone in the Georgia state flag that stands behind Mathis' desk in Albany. The bug was discovered when another employee accidently knocked the flag over, Mathis spokesman said.

Gay had worked for Mathis since the congressman was first elected in 1970.

Gay has been questioned by FBI agents but has not been called before the grand jury, he said in a telephone interview yesterday. He said that he knew of people who had drawn paychecks from Mathis' office and not done any work for the office.

Two of the people Gay mentioned as examples said in telephone interviews yesterday that they had done work for Mathis. Two others Gay named could not be reached.

Asked if Mathis knew of irregularities, Gay said: "He's the only one who puts people on the payroll."

Mathis said Gay is seeking revenge for his dismissal and "has apparently decided to go to any length to discredit and destroy me." A Mathis aide said: "Everybody wants to be a John Dean."

The congressman cited three conversations Gay initiated with employees of the Albany office in which Gay indicated he would take pleasure from Mathis' discomfort. Gay "is relishing what he considers to be my suffering and the suffering of others," Mathis said.

Acting U.S. Attorney Charles Erion in Macon and the Justice Department refused to comment on whether there is an investigation of Mathis' Georgia office.

Gay said yesterday he planted the microphone in the flag because of "a personnel matter in the office." He refused to elaborate but said the microphone was installed "with no malice or intended harm towards" Mathis. He said the microphone was working about six weeks before it was discovered.

After the discovery, Mathis asked all his Georgia employees if they knew how it got in the flag.They all denied having any knowledge, Mathis said.