The Minnesota senator has faced a number of sexual misconduct allegations in recent weeks
A number of Democratic senators in the US have called on their colleague Al Franken to resign from the Senate.
Recent weeks have seen several women accuse Franken - a two-term Minnesota senator and former Saturday Night Live comedian - of inappropriate behaviour and sexual misconduct.
In a lengthy Facebook post, New York Senator Kirsten Gillibrand said she considers Franken "to be a friend" - but suggested he should stand aside.
She observed: "I have spent a lot of time reflecting on Senator Franken’s behavior. Enough is enough. The women who have come forward are brave and I believe them."
While saying Franken's alleged behaviour is 'not the same' as the allegations against other prominent men such as Harvey Weinstein, she stressed "it is still unquestionably wrong, and should not be tolerated by those of us who are privileged to work in public service."
She added: "While Senator Franken is entitled to have the Ethics Committee conclude its review, I believe it would be better for our country if he sent a clear message that any kind of mistreatment of women in our society isn’t acceptable by stepping aside to let someone else serve."
In an apparently coordinated move, several other female Democratic senators also took to social media to call for Franken's resignation:
It is clear that Al Franken has engaged in a pattern of egregious and unacceptable behavior toward women. He should resign.— Sen. Maggie Hassan (@SenatorHassan) December 6, 2017
Sexual harassment and misconduct should not be allowed by anyone and should not occur anywhere. I believe the best thing for Senator Franken to do is step down.— Kamala Harris (@SenKamalaHarris) December 6, 2017
A number of male senators also joined their colleagues in calling for Franken to stand aside:
I agree with my colleagues who have stepped forward today and called on Senator Franken to resign. We can’t just believe women when it’s convenient.— Senator Bob Casey (@SenBobCasey) December 6, 2017
Joe is calling for Senator Franken to resign. pic.twitter.com/ff5i1rnhJs— Senator Joe Donnelly (@SenDonnelly) December 6, 2017
Following an initial allegation that he "forcibly" kissed and apparently groped a radio host, Franken apologised, saying he felt 'disgusted' with himself.
He apologised again late last month as he returned to work after taking a short break in the wake of the allegation.
Washington has been rocked by a number of allegations of inappropriate behaviour by politicians in recent weeks.
Just yesterday, veteran Congressman John Conyers - who had served in the House of Representatives since 1965, making him the longest-serving politician in the House - announced his decision to immediately resign amid allegations of sexual harassment.