After defending the Affordable Care Act outside the U.S. Capitol on Wednesday, the former vice president was asked whether the Obama administration tapped the phones in Trump Tower before the 2016 election.
"Five or six times," Biden said in a deadpan joke, according to NBC News.
"Are you joking? Are you serious?" Biden then said, according to NBC. He added that "any gentleman" would apologize to former President Barack Obama after making that charge.
FBI Director James Comey said Monday he had seen no evidence to support Trump's accusations, leveled in a series of tweets earlier this month. He added at a House Intelligence Committee hearing that the Justice Department asked him to stress that it had not seen information to support the claim.
The bipartisan leaders of the Senate and House intelligence committees also said they had not seen evidence backing the accusation.
Despite Comey's public statement on behalf of the FBI and Justice Department, White House press secretary Sean Spicer said Monday that Trump has no plans to back away from the claim and suggested that all information may not yet be available.
Biden on Wednesday defended the ACA, also known as Obamacare, contending the Republican plan to replace it will not pass. Trump and House Republican leaders are trying to rally support for a bill to repeal parts of the law ahead of Thursday's vote by the House.