The longest-serving member of the United States Congress, John Conyers, said on Sunday that he was stepping down as senior Democrat on the House of Representatives Judiciary Committee, while sexual harassment allegations against him are investigated, Reuters reported.

Conyers said he denied all the allegations, but 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. Conyers is the last member of Congress to have been in office under President Lyndon Johnson in the 1960s.

Last week, the House Ethics Committee said it was investigating allegations of sexual harassment against Conyers, after a staff member alleged that she was fired for refusing to “succumb to sexual advances” from the Michigan Democrat, BBC reported. There were also allegations that Conyers had resolved a harassment case with a payment.

Conyers has maintained that many of the allegations “were raised by documents reportedly paid for by a partisan alt-right blogger”.

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

The US Congress is reviewing policies on how to handle sexual harassment complaints, after a string of such complaints against prominent figures in the US media, Hollywood and politics.