George Stephanopoulos at the 24th annual Broadcasting and Cable Hall of Fame Awards in New York in 2014. (Evan Agostini/Invision/AP)

ABC News chief anchor George Stephanopoulos, already under fire for his contributions to Bill and Hillary Rodham Clinton’s charitable foundation, served as a moderator and awards judge for an arm of the organization for years without disclosing those roles to viewers.

Stephanopoulos was among a number of well-known TV news figures and columnists who have volunteered to help the Clinton Global Initiative (CGI), an offshoot of the Clinton Foundation that convenes meetings to discuss domestic and international issues.

A former campaign aide and White House adviser to President Bill Clinton, Stephanopoulos has apologized repeatedly since last week for contributing $75,000 to the Clinton Foundation between 2012 and 2014. He has acknowledged that the contributions created an apparent conflict of interest, given that he will be ABC’s chief political correspondent during a campaign in which Hillary Clinton is a leading candidate.

But Stephanopoulos has not to date disclosed lending his name to panels organized by CGI, which convenes world leaders for conferences.

Stephanopoulos was a panel moderator in 2006 and a panelist in 2008 and 2009 at CGI’s annual conference, according to Peter Schweizer, the author of “Clinton Cash,” a book about the Clintons’ finances. He also served as a judge with Chelsea Clinton in 2013 and 2014 on a CGI contest.

The ABC News anchor did not disclose those roles or his financial contributions when he grilled Schweizer about his book last month on his Sunday morning program, “This Week with George Stephanopoulos.”

ABC News spokeswoman Heather Riley said Stephanopoulos’s involvement with CGI was disclosed to ABC News executives, who considered it “all aboveboard.” She said his activities did not violate any internal policies.

Riley declined to comment on whether he should disclose his past association with CGI to viewers or whether he would be compelled to do so if he has further involvement with the Clinton-affiliated organization.

Riley asked in an e-mail, however, “Did you ask every other journalist that moderated panels for CGI if they disclosed this to their audiences? Only seems fair if you’re posing that question to us.”

CGI lists a number of TV anchors, correspondents and commentators as “Notable Past Members,” including Christiane Amanpour and Anderson Cooper of CNN; columnists Thomas Friedman and Nicholas Kristof of the New York Times; Matt Lauer and Tom Brokaw of NBC; Greta Van Susteren of Fox News; Katie Couric (then of CBS); and Judy Woodruff of “PBS Newshour.”

Unlike Stephanopoulos, none of the other media figures were previously employed by one of the Clintons. Woodruff has acknowledged giving $250 to the Clinton Foundation in 2010.

“We’ve been raising questions about these Clinton conference involvements for years,” said Tim Graham, director of media analysis for the Media Research Center, a conservative watchdog organization based in Reston, Va. While Graham acknowledged that other journalists have participated in Clinton-related events, he said Stephanopoulos’s involvement goes deeper, such as judging contests with Chelsea Clinton.

“He should be held to a stricter standard than other Clinton-friendly reporters,” Graham said. “He seems completely oblivious to appearances of a conflict of interest.”