Franken: 'We don't know what the Russians have on Donald Trump' The senator said a probe is needed to uncover what Russia may have 'over' Trump.

 -- Democratic Sen. Al Franken said President Trump’s assertion that former President Obama tapped his phones at Trump Tower during the 2016 election campaign are “just ridiculous and a distraction."

“This is just a distraction, to distract from this very, very serious interference by a foreign power on our democracy and the question of whether Trump world -- his campaign, his business associates -- had anything to do with it and colluding with them,” the Minnesota senator told ABC News chief global affairs correspondent Martha Raddatz on "This Week" on Sunday.

Franken, who has called for an independent investigation into questions around Russia and Trump campaign associates, said: "Here's what I want to get to.

His own son, Donald Trump's son, has said in 2008, that Russia did an inordinate amount of business with them. And we don't know what they have over him. We don't know what the Russians have on Donald Trump. And we need -- and we need to see, if anything -- we need to see his tax returns.

Raddatz noted that it was Franken, a Senate Judiciary Committee member, who asked Attorney General Jeff Sessions during his Jan. 10 confirmation hearing about allegations that Trump associates communicated with Russian officials during the presidential campaign.

Sessions told the Judiciary Committee he “did not have communications with the Russians.”

“That turned out not to be true,” Franken told Raddatz. “He was testifying under oath to the American people and he said something that just wasn’t true.”

It was revealed last week that during the campaign Sessions, who was then a senator on the Armed Services Committee and also working to help Trump's candidacy, had spoken twice to Russia's ambassador to the U.S. In the wake of these reports, the attorney general recused himself from any investigations around Russia's alleged interference in the election or its contacts with Trump associates.

Franken, however, has not like some other Democrats called for Sessions to resign. The senator also told Raddatz that he doesn't want to call Sessions' apparently mistaken testimony to the Senate perjury.

“I don’t want to go there definitively and say that we should be prosecuting the attorney general,” Franken said. But he said Sessions “owes it to the Judiciary Committee to come back and explain himself.”

Franken said he has asked Sessions to come back before the committee but he said he has yet to get a response.