The president's comments come as Reps. Devin Nunes, R-California, and Adam Schiff, D-California, the chairman and ranking member of the House Intelligence Committee, announced that they were provided no evidence to support the allegation.
Both Nunes and Schiff agreed that Trump was likely incorrect if one were to take his claims literally, but Nunes acknowledged the "concern that the president has about other people, other surveillance activities looking at him or his associates."
Trump also offered his first reaction to the leaked portion of his 2005 tax returns in the interview with Carlson, calling the report "illegal" and "a disgrace."
"I have no idea where they got it," said Trump. "But it’s illegal and they’re not supposed to have it and it's not supposed to be leaked."
Independent journalist David Cay Johnston obtained the purported first two pages of the return and made them public Tuesday night, showing Trump paid $38 million in federal taxes on income of more than $150 million in 2005.
"It’s certainly not an embarrassing tax return at all," Trump said. "But it’s an illegal thing; they’ve been doing it, they’ve done it before and I think it’s a disgrace."
Trump is referring to a previous leak of a portion of his 1995 tax returns provided to The New York Times showing that Trump took a $916 million loss that "would have been large enough to wipe out more than $50 million a year in taxable income over 18 years.” However, the portion of the 2005 returns revealed Trump did, in fact, pay an effective tax rate of 25 percent that year.
The White House has not yet specified whether his 2005 returns fall into the category of being under audit and hasn't said whether it will now release the full returns now that the initial portion has been revealed.