TALLAHASSEE, Fla. (AP) - Despite warnings that it violates the U.S. Constitution's First Amendment, a Florida House panel April 4 narrowly approved a bill requiring newspaper editorial board members to publicly disclose their finances.

The bill, sponsored by Rep. Bruce McEwan, R-Orlando, would also make it a second-degree misdemeanor for a newspaper to publish any editorial unless it is signed by the author.

A subcommittee of the House Judiciary Committee approved the measure on a 4-3 vote. It would include editorial board members in a present law requiring state employees to file financial disclosure forms by July 1 every year or face a possible $5,000 fine.

One of the 32 co-sponsors of the bill, Rep. Elvin Martinez, D-Tampa, said the measure is not a vendetta against newspapers but rather an attempt to shed more light on their role as public opinion leaders.

''The real molder of public opinion is the press,'' Martinez said. ''They can take you and beat you and do anything to you, and they're immune. I think people have a right to know if their views are jaundiced by some financial interest.''

Barry Richard, attorney for the Florida Press Association, said the measure clearly infringes on the First Amendment's guarantee of a free press and would never stand up in court.

''The only justification for it is that the person (editorialist) makes public comment,'' he said. ''Are we next going to include the League of Women's Voters and other groups in this category?''

McEwan said his intention is not to violate the First Amendment.

''There's nothing in this bill to prohibit freedom of the press,'' he said.

Rep. John Cosgrove, D-Miami and chairman of the Court Systems, Probate and Consumer Law subcommittee, said some lawmakers supported the bill simply to take a stab at the press.

''As much as I might want to get in there and make a little jab at editorial boards, I think the greater freedom of expression is more important,'' Cosgrove said.

The legislation next moves to the full House Judiciary Committee, which did not immediately set a date to consider it. McEwan said he was optimistic of approval.

Richard was not so sure.

''It's press-bashing,'' he said. ''It depends on how many people are willing to put their names on something that's blatantly unconstitutional.'' Union Chief Sues Daily News Over Remark

NEW YORK (AP) - The president of the mailers union sued the Daily News, one of its officers and its Chicago-based parent for $30 million on April 5, claiming they had damaged his reputation as a labor leader.

The libel suit, filed by George McDonald, president of the mailers union and the Allied Printing Trades Council, names John T. Sloan, the News' vice president for human resources, and the Tribune Co. It seeks $5 million in compensatory damages and $25 million in punitive damages.

The 10 unions in the council are involved in tense negotiations with the News over new contracts; the old contracts expired March 30.

Sloan said he had not received the suit and thus had no comment.

According to the suit, McDonald enjoyed a national reputation ''as a dedicated, honest, reputable, loyal and highly competent labor leader.''

That reputation was damaged, the suit said, by remarks Sloan made to the media on March 15 that McDonald gave away work to another union that traditionally was performed by the mailers union.

In a related development, Local 3 of The Newspaper Guild asked that News Publisher James Hoge negotiate directly with the Guild because the News' negotiators were not familiar with the territory and the talks were proceeding slowly.

Robert Ballow, a Nashville, Tenn.-based attorney, has been the News' lead negotiator.

Sloan said he did not get an immediate response to the request. Newspaper Sues Union Official Who Filed Libel Lawsuit

SAN JOSE, Calif. (AP) - The San Jose Mercury News on March 29 filed a lawsuit against the former chief of the San Jose hotel workers union, claiming his 1983 libel lawsuit against the newspaper was a violation of free press rights.

The newspaper claimed the lawsuit filed by Frank Marolda damaged its reputation and is asking for $1 million in damages and recovery of ''a significant amount'' for legal fees.

''It's a combination of abuse of the process and malicious prosecution,'' said Edward Davis, attorney for the newspaper. ''The union's lawsuit was designed to send out a message to everyone else that if you write a negative story about the union, you're going to be in trouble.''

In late 1987, a Santa Clara County judge threw out Marolda's lawsuit against the paper and two of its reporters.

Marolda, then president of a Hotel and Restaurant Employees and Bartenders Union local in San Jose, and the union objected to an article that appeared Oct. 24, 1982.

The story described Marolda's administration of the union and his problems connected to a U.S. Senate investigation of labor corruption.

The newspaper's suit alleges that Marolda and the union ''brought the action for the purpose of harassing, annoying, embarrassing, and otherwise oppressing the Mercury News.'' Bee Victim of April Fool's Gag on 'Victim's' Birthday

FRESNO, Calif. (AP) - The Fresno Bee says it was the victim of an April Fool's Day trick by someone who falsely reported a man's death.

''I thought it was a joke until I started getting phone calls,'' said Vern Elwood Elston, whose obituary ran April 1, his 38th birthday. ''Then I realized how serious it was. It didn't go over too well with my family.''

The Bee said the obituary was delivered March 31 on a form it furnishes to funeral homes.

Managing Editor Donald Slinkard said the newspaper will strengthen its procedures to avoid a repeat of such a hoax.

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