Sen. Jeff Flake Jeffrey (Jeff) Lane FlakeRepublican former Michigan governor says he's voting for Biden Maybe they just don't like cowboys: The president is successful, some just don't like his style Bush endorsing Biden? Don't hold your breath MORE (R-Ariz.) on Monday called for President Trump to apologize for his claim that former President Barack Obama Barack Hussein ObamaThe Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon Trump appointees stymie recommendations to boost minority voting: report Obama's first presidential memoir, 'A Promised Land,' set for November release MORE wiretapped Trump Tower before the election, which the FBI and National Security Agency said this week is unsubstantiated.

During an interview on "Mac & Gaydos" on KTAR Arizona radio, Flake was questioned about whether Trump should admit his claims, first sent out over Twitter, were wrong, CNN reported.

"I think that ought to happen and we ought to move on," said Flake, a frequent Trump critic.

The president has refused to back down from the accusation, even as congressional Republicans and intelligence officials call it unfounded.

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On Monday, FBI Director James Comey said the Department of Justice has "no information" to support the idea that Obama spied on Trump. Comey refused to "characterize" the tweets containing the allegations from the president, saying only that "I have no information" that supports the claim.

Flake during the interview said the wiretapping claim is a "serious allegation that you make about somebody."