ABC news host George Stephanopoulos admitted Thursday he had donated $75,000 to the Clinton Foundation and did not disclose this conflict of interest to viewers before interviewing the author of a book critical of the foundation's foreign donors and influence over Hillary Clinton at the State Department.

Stephanopoulos, a former Bill Clinton communications aide, interviewed Clinton Cash author Peter Schweizer on the April 26 edition of This Week, where he pushed back against his reporting and Schweizer himself, repeating Democratic attacks that he had a "partisan interest" in disparaging the Clintons.

"They say you used to work for President Bush as a speech writer. You are funded by the Koch brothers," he said. "How do you respond to that?"

"As you know, the Clinton campaign says you haven't produced a shred of evidence that there was any official action as secretary that supported the interest of donors," he asked later. "We’ve done investigative work here at ABC News, found no proof of any kind of direct action. An independent government ethics expert at the Sunlight Foundation Bill Allison wrote this: ‘There's no smoking gun. No evidence that the changed policy based on donations to the foundation. No smoking gun.' Is there a smoking gun?"

Stephanopoulos did not point out that the Sunlight Foundation is funded by left-wing billionaire George Soros.

In an interview with Comedy Central's Jon Stewart after his interview of Schweizer, Stephanopoulos called the case of allegations against the Clinton Foundation "a tough one."

"I read the book that this is based on, Clinton Cash, and I actually interviewed the author on Sunday," he said. "This is a tough one. Because when you actually look at, look closely at it, he even says there is no evidence of any direct action taken on behalf of the donors … But everybody also knows when those donors give that money, President Clinton or someone, they get a picture with him, there is a hope that is going to lead to something."

Both men laughed earlier in the interview when Stewart whether Stephanopoulos was "familiar with the Clintons."

The story came to light when the Free Beacon‘s Andrew Stiles discovered Stephanopoulos' donation and requested a comment from ABC News. Stephanopoulos then confirmed the donation to Politico and issued an apology for not disclosing it beforehand, and ABC announced it would not take any punitive action against him.

UPDATE: 2:37 P.M.: This story has been updated to reflect Stephanopoulos donated $75,000, not $50,000.