But Stephanopoulos left a key detail out of his reporting -- that he has donated to the foundation.
The network news star gave a total of $75,000 to the foundation in 2012, 2013 and 2014. The amount was first reported as $50,000.
Stephanopoulos made no mention of the contributions during a segment of the program "This Week" in which he aggressively questioned Peter Schweizer, the author of "Clinton Cash," a recently published book that lays out allegations about potential conflicts involving Clinton Foundation donors.
On Thursday, Stephanopoulos apologized in a statement and said he would not moderate the GOP debate ABC is hosting in New Hampshire in February.
"I made charitable donations to the Foundation in support of the work they're doing on global AIDS prevention and deforestation, causes I care about deeply," he said. "I thought that my contributions were a matter of public record. However, in hindsight, I should have taken the extra step of personally disclosing my donations to my employer and to the viewers on air during the recent news stories about the Foundation. I apologize."
His decision not to moderate the debate came after Sen. Rand Paul threatened to boycott the event. Others called for Stephanopoulos to recuse himself from all coverage of 2016, which he said he would not do.
The controversy gives new fuel to critics of Clinton as well as Stephanopoulos. The anchor was a top aide to President Clinton in the 1990s but has worked to shed that partisan affiliation over many years in television news.
Hillary Clinton's presidential campaign embraced his tough questioning of Schweizer during the "This Week" segment, in which Stephanopoulos repeatedly made the point that the author had revealed no criminal activity or "smoking gun."
ABC News said there would be no punishment for Stephanopoulos.
"As George has said, he made charitable donations to the Foundation to support a cause he cares about deeply and believed his contributions were a matter of public record," the network said in a statement first reported by Politico.
"He should have taken the extra step to notify us and our viewers during the recent news reports about the Foundation. He's admitted to an honest mistake and apologized for that omission. We stand behind him."
Reactions to ABC's move broke largely along partisan lines that also revealed two very different views of the Clinton Foundation. Supporters tend to depict the foundation as primarily a charity that only incidentally provides support to the Clintons' personal projects. Critics portray it as mostly a vehicle for the Clintons to promote their political ambitions.
Critics of ABC noted that in 2010, MSNBC suspended then-host Keith Olbermann for donating to Democratic congressional candidates, which was a violation of the network's ethics policy. Supporters said that donations to political candidates and donations to a charity are two very different things.
Schweizer, meanwhile, is having problems of his own. His publisher revealed that errors in the text of "Clinton Cash" merited considerable corrections. Late Monday, readers who had purchased the book on Kindle were alerted that "significant revisions have been made" and they could download the corrected draft free of charge.