BOSTON (AP) _ Hometown support for Rep. Barney Frank has dwindled markedly since he admitted employing a male prostitute he'd previously hired for sex, according to a survey published Tuesday.

Of 300 registered voters polled, 74 percent said they would have voted for Frank before the disclosure of his relationship with Stephen L. Gobie, but 56 percent of them said they now would vote to return him to Congress.

''If congressional elections were held last week, over one-half of Newton's voters would choose to re-elect ... Frank, but his hometown support has slipped significantly,'' The Tab weekly newspaper study concluded.

Frank's district includes the Boston suburb of Newton, his hometown.

Sixteen percent of those polled Oct. 2 said they would not have voted for Frank before the relationship was disclosed in August. That number grew to 23 percent following the disclosures, the survey said.

Frank spokesman Douglas Cahn declined to comment Tuesday on the survey.

Of the poll participants, 47 percent said they would not vote for Frank because of his admitted poor judgment in his relationship with Gobie; 19 percent cited Frank's admission he hired a prostitute; and 7 percent noted his sexual preference.

But 37 percent of those questioned said the above factors would not sway their votes, according to the poll conducted by First Research of Boston.

The telephone survey, with a margin of error of plus or minus 6 percent, questioned 132 registered Democrats, 134 Independent and non-affiliated voters and 36 Republicans.

A spokeswoman for the local election commission said the breakdown for 46,582 registered voters as of April 1 was 23,109 Democrats, 18,203 Independent and non-affiliated voters and 5,270 Republicans.

Frank, a five-term Democratic congressman and outspoken liberal who was re- elected overwhelmingly in 1988 after disclosing his homosexuality, sent a letter to constitutents last month apologizing for ''some serious mistakes in judgment years ago.''

The House ethics committee has scheduled an inquiry into Frank's 18-month relationship with Gobie, who went public in August with his claims he ran a prostitution ring out of the congressman's Capitol Hill apartment.

Frank has acknowledged paying Gobie for sex and then hiring him as a personal assistant and driver, but says he threw Gobie out in August 1987 when he learned of the prostitution operation.