US Attorney General Jeff Sessions never gave Donald Trump any reason to believe his campaign was wiretapped, he has said.
"My answer is no,” the American government's chief lawyer told a news conference when he was asked whether he had led the US leader to believe he was under surveillance by the Obama administration.
He added that because he was “active” in the presidential campaign, he was barred from investigations about the alleged bugging.
“Even though you may have had nothing whatsoever to do with anything improper, you should not investigate your own campaign, so I have recused myself and am unable to comment on any of these details,” Mr Sessions said.
“I'm not talking to the president or the people who are investigating the case. And I'm unable to comment on any of these details.”
Mr Trump accused his predecessor of wiretapping the phones in New York's Trump Tower - which served as his headquarters during his presidential campaign - in a string of Twitter posts earlier this month.
He failed to provide any evidence for the claim, which Mr Obama has strenuously denied.
The Trump administration came under pressure after a congressional committee investigating the allegation said it had found no evidence to support it and said it did not believe it happened.
But earlier this week Mr Trump had said he was “very confident” he would be vindicated.
Mr Sessions is the latest in a line of Republican's to dispute Mr Trump's claims.
Devin Nunes, the Republican Chairman of the House Intelligence Committee, has also said he did not believe the President's phones had been tapped.
“As I told you last week, in regard to the president talking about tapping Tower. That evidence still remains the same. We don’t have no evidence that took place,” he said.
“And I don’t believe, having spoken to people just in the last week, I don’t believe there was an actual tap of Trump Tower.”
White House Press Secretary Sean Spicer also appeared to walk back on the claims, when he insisted that the President was not referring to wire tapping specifically, but rather "surveillance and other activities".