The House of Representatives has held US Attorney General Eric Holder in criminal contempt of Congress for failing to provide documents related to a failed gun-tracking operation. It is the first time a sitting Cabinet member has been held in contempt.
The vote was 255-67, with more than 100 Democrats boycotting. They said the contempt resolution was a political stunt.
Republicans accuse Mr Holder, the top US lawyer, of stonewalling the investigation of "Operation Fast and Furious" in which guns purchased in the United States were taken to Mexico. Democrats charge the vote was politically motivated ahead of the November election in which their leader President Barack Obama is seeking a second term.
The consequences of Thursday's House vote are not clear. Criminal charges are unlikely because the matter will be referred to a prosecutor under Mr Holder. A separate vote on civil contempt could trigger a potentially lengthy lawsuit.
In past cases, courts have been reluctant to settle disputes between the legislative and executive branches.