US Democratic Senator Al Franken, once tipped as a future presidential candidate, apologized profusely to a female radio host he is accused of groping and welcomed a congressional investigation into his conduct Thursday.

Sports broadcaster and former model Leeann Tweeden accused the former comedian of touching her while she slept and kissing her without her consent in 2006 -- the latest in a string of sexual assault allegations against prominent American men.

Franken's rise from funnyman to darling of the political left was thrown into serious doubt by the shock allegations and the likely opening of a Senate ethics investigation that could see him fined, striped of committee posts or even expelled.

Tweeden revealed the allegations in a wrenching first person article that included a photo of Franken groping her breasts while she was asleep in body armor and helmet on a military flight.

She said the incident occurred when they were both on a tour entertaining US troops deployed in Afghanistan.

"I felt violated" she wrote on the website of KABC radio in Los Angeles, where she hosts a show, "Embarrassed. Belittled. Humiliated."

"How dare anyone grab my breasts like this and think it's funny?"

Amid criticism from left and right, Franken, aged 66 and married for more than four decades, issued a full throated apology and acknowledged the veracity of the photo.

"I don't know what was in my head when I took that picture, and it doesn't matter. There's no excuse," he said in a statement.

"I look at it now and I feel disgusted with myself. It isn't funny. It's completely inappropriate. It's obvious how Leeann would feel violated by that picture."

Tweeden said Franken, at the time a prominent comedian, writer and liberal talk radio host who had risen to fame on the satirical show Saturday Night Live, had also written a sketch in which he was meant to kiss her on stage in front of the troops.

During rehearsals for the comedy turn, Tweeden said Franken "came at me, put his hand on the back of my head, mashed his lips against mine and aggressively stuck his tongue in my mouth."

Tweeden said nobody witnessed the incident, and that she immediately pushed Franken away and went to wash out her mouth, feeling "disgusted and violated."

Franken said he does not "remember the rehearsal for the skit as Leeann does" but said "I understand why we need to listen to and believe women’s experiences."

"I am asking that an ethics investigation be undertaken, and I will gladly cooperate."

Mitch McConnell, the Republican majority leader in the Senate, called for the chamber's Ethics Committee to review the matter, "as with all credible allegations of sexual harassment or assault.

"Regardless of party, harassment and assault are completely unacceptable -- in the workplace or anywhere else."

The top Democrat in the Senate, Chuck Schumer, joined in calling for the committee to "fully investigate this troubling incident," saying in a statement that "sexual harassment is never acceptable and must not be tolerated."

Senate ethics investigations are rare but not unheard of.

Sanctions could include written warnings, removal from key party or committee posts, and, under extreme circumstances, expulsion from the Senate. That would be highly unlikely, as expulsion requires a two-thirds vote in the chamber.

Source: AFP