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WASHINGTON (Reuters) - U.S. Representative John Conyers is stepping down as senior Democrat on the House of Representatives Judiciary Committee, while lawmakers investigate allegations of sexual harassment against him, Conyers said in an emailed statement on Sunday.

Conyers said that while he denied the allegations, his presence during a congressional ethics review of the matter was a distraction.

“I cannot in good conscience allow these charges to undermine my colleagues in the Democratic Caucus, and my friends on both sides of the aisle in the Judiciary Committee,” Conyers said.

Conyers, 88, from Michigan, is the longest-serving House lawmaker and a founding member of the Congressional Black Caucus.

The House Ethics Committee said last week it was investigating allegations of sexual harassment against Conyers, who said his office had resolved a harassment case with a payment but no admission of guilt.

The allegations against Conyers came to light as Congress reviews policies on how to handle sexual harassment complaints. They followed a string of such complaints against prominent figures in the U.S. media, Hollywood and politics.

“In this case, I expressly and vehemently denied the allegations made against me and continue to do so,” said Conyers.

Twelve women who said they previously worked for Conyers told reporters in a statement on Sunday that he “was a gentleman and never behaved in a sexually inappropriate manner in our presence.” The group said it supported letting the ethics probe run its course.

House Democratic leader Nancy Pelosi called for “zero tolerance” on sexual harassment in a statement released after Conyers’ email. “We are at a watershed moment on this issue, and no matter how great an individual’s legacy, it is not a license for harassment.”