WASHINGTON (Reuters) - U.S. Democratic Senator Al Franken returned to Congress on Monday to begin what he called a process of rebuilding trust shattered by allegations he had groped or inappropriately touched women, vowing “this will not happen again.”

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“I know that I am going to have to be much more conscious when in these circumstances, much more careful, much more sensitive and that this will not happen again going forward,” he told reporters outside his office on Capitol Hill.

Franken has been accused of sexual misconduct by Leann Tweeden, a radio broadcaster who in 2006 appeared with Franken in an entertainment tour for U.S. troops serving in war zones.

Prior to winning his Senate seat, Franken was a well-known comedian, television writer and author.

Another woman, Lindsay Menz, accused Franken of touching her buttocks when they were being photographed at the Minnesota State Fair in 2010.

A contrite Franken appeared on Monday before a throng of reporters gathered outside his office as the senator vowed to get back to work following a week-long Senate Thanksgiving break.

“I know there are no magic words that I can say to regain your trust and I know that’s going to take time. I’m ready to start that process and it starts with going back to work today,” Franken said, apparently addressing his Minnesota constituents back home.

Franken, first elected in 2008, is not due to run for a third Senate term until 2020.

Following sexual misconduct allegations against movie producer Harvey Weinstein, additional complaints have been made regarding other big names in entertainment and in politics, notably Republican U.S. Senate candidate Roy Moore of Alabama, and Representative John Conyers of Michigan.

All three men have denied the allegations, which Reuters has not been able to verify, and Conyers has stepped down as senior Democrat on the House of Representatives Judiciary Committee.

In November, 2008, Franken barely won election in a race so close that it took vote recounts and court rulings before he finally was declared the winner the following July.

Because of the closeness of his race and his background in entertainment and not government service, Franken came to the Senate refusing most media interviews. He kept a low profile while he tried to demonstrate to constituents that he was serious about his new political career.

Eight years later, Franken is again having to prove himself with Minnesotans.

Noting that his supporters had “counted on me to be a champion for women,” Franken again apologized for his behavior.

In response to a reporter’s question, he said he would be “open” to making public the findings of a Senate ethics probe once that process is complete.