State Sen. Jerome F. Connell, chairman of one of the Maryland General Assembly's powerful committees, is under investigation by federal prosecutors and the Internal Revenue Service, and has turned over major portions of his law firm's financial records to them in the last several months, according to sources.

Prosecutors requested the law firm's records covering the years 1979 to 1981 from Connell in March and reportedly have subpoenaed at least two of Connell's clients to appear before a federal grand jury in Baltimore next week. Connell apparently has not been subpoenaed.

The investigation reportedly involves the Anne Arundel County liquor board.

Connell, 55, an Anne Arundel County Democrat, assumed the chairmanship of the Senate's Economic Affairs Committee during this past session and was the leading proponent of the sweeping banking deregulation bill recently signed into law by Gov. Harry Hughes.

Reached yesterday, the three-term senator, who was reelected last year by fewer than 150 votes, said he had no comment on the reported investigation. Federal prosecutors in the U.S. Attorney's office in Baltimore refused yesterday to confirm or deny that an investigation of Connell exists.

Sources said yesterday that the investigation has been going on for at least six months and that it is related to Connell's involvement with a number of restaurant owners who have come before the liquor board seeking licenses. State senators are generally considered influential with the liquor boards in their home counties.

Yesterday, sources close to Connell confirmed that several restaurant owners whom Connell represented in the past recently called him to say they had been questioned by the prosecutors.

Connell, a tough-talking chain-smoker, is considered one of the brightest members of the legislature, a man known for his brusque style. First elected to the House of Delegates in 1966, he is a product of the northern Anne Arundel County Democratic clubs, the traditional spawning grounds of conservative, north county Democrats.