WASHINGTON — Lawmakers from both parties are making a new effort to pass a federal shield law to protect reporters from being forced to reveal their sources.

The bill, co-sponsored by Republicans and Democrats in both the House and Senate, would write into federal law the protection for reporters now granted by more than 30 states and the District of Columbia.

Such protection, First Amendment advocates say, would give government whistleblowers more reason to reveal corruption when they know that reporters will be shielded in most cases from prosecutors’ efforts to reveal information.

“The protections provided by the Free Flow of Information Act are necessary so that members of the media can bring forward information to the American public without fear of retribution or prosecution,” U.S. Rep. Mike Pence, R-Ind., said in a prepared statement.

Anticipating objections from the Bush administration, the sponsors have included exceptions that would apply if the judge in a case determined the public interest in disclosing the source outweighed the public interest in newsgathering, said Rep. Rick Boucher, D-Va., who with Pence is one of the lead sponsors of the bill.

For example, a judge could require a reporter to reveal a source to prevent imminent death or harm to national security.

The bill is co-sponsored in the Senate by Sens. Chris Dodd, D-Conn., and Dick Lugar, R-Ind.