Ethics Committee Chief Counsel and Staff Director John Sassaman said allegations by Sen. David Vitter, R-La., lacked evidence or other information to support them, Roll Call reported Tuesday.
"The committee has previously concluded that mere allegations, with no evidence or information to support their substantive merit, are insufficient to extend the committee's investigative process," Sassaman wrote.
Sassaman relayed the determination in a letter to Vitter, in which he noted that Vitter didn't provide evidence that Boxer and Reid had anything to do with the alleged misconduct.
Vitter alleged Boxer and Reid engaged in improper conduct by floating an amendment about barring congressional members from accessing federal benefits in the healthcare exchanges under the Affordable Care Act if they engaged in prostitution.
Vitter was linked to the investigation involving Deborah Jeane Palfrey, the so-called D.C. Madam. The possibility of the amendment was seen as retaliation to Vitter's attempt to get a vote on an amendment to an energy efficiency bill about employer contributions for healthcare for members and staff.