The former president referenced a CNN report detailing Sanders' fundraising for the Democratic Senatorial Campaign Committee at large donor events.
"I practically fell out of my chair when I saw it," Bill Clinton said, according to the New York Times.
He also brought up the "sexist" attacks Hillary Clinton's supporters have been subject to from some backing Sanders' presidential bid, sharing the story of one Clinton supporter's experience online.
"She and other people who have gone online to defend Hillary, to explain why they supported her, have been subject to vicious trolling and attacks that are literally too profane often, not to mention sexist, to repeat," Bill Clinton said, according to the New York Times.
Sanders on Sunday addressed the "Bernie bros," his supporters who launch sexist attacks on backers of Hillary Clinton.
"I have heard about it. It's disgusting," Sanders told CNN on Sunday. "Look, we don't want that crap. ... We will do everything we can and I think we have tried. Look, anybody who is supporting me that is doing the sexist things is -- we don't want them. I don't want them. That is not what this campaign is about."