In a blow to Mayor Bloomberg’s campaign against illegal guns, a Senate committee yesterday voted 19–10 to pass an amendment that mandates prison time for police officers who use federal gun-trace data for anything except specific investigations.

Mr. Bloomberg responded to the vote with a harsh statement, saying the senators who voted for the amendment made America less safe.

“Today’s vote … showed Congress at its most craven, buckling to pressure from the gun lobby to protect those who traffic in illegal guns — even if it means locking up police officers,” he said. The new amendment will “empower criminals, undercut cops, and endanger innocent citizens,” he said.

Senator Shelby, a Republican of Alabama, sponsored the amendment, which is a more strongly worded version of an amendment sponsored by Rep. Todd Tiahrt, a Republican of Kansas. That amendment has been renewed annually for the last three years.

Mr. Bloomberg’s aides said the Shelby amendment would prevent police departments from releasing aggregate trace data to mayors and would mandate five years in prison for any police officer who uses the data for anything except a criminal investigation.

Mr. Shelby said in his prepared remarks to the committee that Mr. Bloomberg’s decision to send undercover investigators into southern states last year “jeopardized” ongoing investigations by the Bureau of Alcohol, Tobacco, Firearms, and Explosives.

Members of the House Appropriations Committee will vote on a version of the Tiahrt amendment in the second week of July.