(CNN) - San Diego's Democratic mayor Bob Filner, currently undergoing "intensive counseling" after being accused of sexually harassing more than a dozen women, should resign his post, Sen. Barbara Boxer wrote in a personal letter to the mayor Friday.
Addressing Filner simply as "Bob," Boxer – who is also a Democrat - wrote, "We've known each other for a long time…So I am speaking to you now on a personal and professional level, and asking you to step down as mayor and get the help you need as a private citizen."
She noted in the missive that she had already made public calls for the embattled San Diego mayor to step down.
"But now I must say this directly to you: Bob, you must resign because you have betrayed the trust of the women you have victimized, the San Diegans you represent and the people you have worked with throughout your decades in public life," she wrote.
Her letter comes nearly two weeks after her fellow U.S. senator, Dianne Feinstein, told CNN chief political correspondent Candy Crowley that Filner had lost all moral authority, and thus could no longer lead his city.
"Being the mayor of a big city, you're a role model for people," Feinstein said on "State of the Union." "You're either inspirational to people or you aren't. It's a very tough job. And I don't think that somebody who is lacking a moral compass really sets a role model or really will provide the kind of leadership that San Diegans want."
At the end of July, Filner announced he would take a two-week hiatus from his job while undergoing "intensive counseling" in response to the sexual harassment allegations.
He said he would remain engaged with city business while in therapy, and that he would return to office on August 19.