In a jarring photo, Franken is seen pretending to grope radio anchor Leeann Tweeden while she is asleep on a return flight from Afghanistan.
"I was belittled and humiliated," Tweeden said Friday in an interview on "Good Morning America." "And that's never funny."
Tweeden also claimed Franken, at the time a comedian, forced her to rehearse a kissing scene for a skit he had written.
"He mashed his lips against my face," Tweeden said at a Thursday press conference. "And he stuck his tongue in my mouth so fast."
The controversy now potentially threaten's Franken's political career.
Franken said he doesn't remember the rehearsal as Tweeden does, but he apologized in a statement.
"There's no excuse," he said of the photo. "I look at it now and feel disgusted with myself. It isn't funny. It's completely inappropriate. It's obvious how Leeann would feel violated by that picture."
Tweeden described the apology as heartfelt.
"I do accept it," she said. "I think he realized how people felt about it. Now it's a different time - 2006 is not 2017.
President Donald Trump, who has remained silent about the multiple accusations of sexual misconduct against Alabama Senate candidate Roy Moore, tweeted about Franken on Thursday evening.
The Al Frankenstien picture is really bad, speaks a thousand words. Where do his hands go in pictures 2, 3, 4, 5 & 6 while she sleeps? .....— Donald J. Trump (@realDonaldTrump) November 17, 2017
"The Al Frankenstien picture is really bad, speaks a thousand words," Trump wrote. "Where do his hands go in pictures 2, 3, 4, 5 & 6 while she sleeps? ....."
Franken said he would support a Senate ethics investigation into his behavior.
ABC News and The Associated Press contributed to this report.