Donald Trump escalated his war with Barack Obama as a committee in Congress agreed to look into his claims that the former president and his administration abused executive powers in last year’s election.
In his latest high-stakes salvo, and as he prepared to roll out a revised travel ban on Muslim-majority countries, Mr Trump had called for a congressional investigation after alleging that he was the victim of a dirty tricks campaign akin to Watergate.
His move came a day after he claimed his predecessor ordered a wiretap of the phones at Trump Tower in New York, Mr Trump’s campaign headquarters.
James Comey, the FBI director, asked the Justice Department this weekend to publicly refute Mr Trump’s assertion, unnamed officials told the New York Times on Sunday.
Neither the FBI nor the Justice Department have so far released any public statement.
Mr Obama has said the allegations made against him by Mr Trump were "simply false". James Clapper, his former intelligence chief, also "absolutely denied" the claims. But Mr Trump told a friend he was convinced he would be "proven right".
Christopher Ruddy, chief executive of Newsmax Media and a Trump donor, said he had spoken to the president twice at the weekend about the wiretap allegations.
Mr Ruddy said: "I haven’t seen him this p----- off in a long time. When I mentioned Obama 'denials' about the wiretaps he shot back 'This will be investigated, it will all come out. I will be proven right'."
Sean Spicer, the White House press secretary, said reports concerning potentially politically motivated investigations were “very troubling".
He said: "President Trump is requesting that as part of their investigation into Russian activity, the congressional intelligence committees exercise their oversight authority to determine whether executive branch investigative powers were abused in 2016."
(1/4) Reports concerning potentially politically motivated investigations immediately ahead of the 2016 election are very troubling.
— Sean Spicer (@PressSec) March 5, 2017
Congressman Devin Nunes, chairman of the House Intelligence Committee, responded by confirming that his committee "will make inquiries into whether the government was conducting surveillance activities on any political party’s campaign officials or surrogates”.
The committee is already examining possible links between Russia and Mr Trump’s campaign.
Tom Cotton, a member of the Senate Intelligence Committee, said it would also investigate Mr Trump's allegations.
He said: "We're going to follow the facts wherever they lead us and I'm sure that this matter will be a part of that inquiry."
Mr Trump offered no evidence and is believed to have based the claims, made in a series of tweets on Saturday, on press reports.
Those reports suggested the FBI had a warrant from a secret court to carry out electronic surveillance at Trump Tower.
Who was it that secretly said to Russian President, "Tell Vladimir that after the election I'll have more flexibility?" @foxandfriends
— Donald J. Trump (@realDonaldTrump) March 5, 2017
Press reports stretching back to November suggested the FBI obtained a warrant under the Foreign Surveillance Act (FISA) to conduct the surveillance towards the end of the election campaign.
At the time the agency was looking into possible communications between a Trump Organization computer server and Alfa Bank, a Russian bank.
The FBI did investigate but concluded the communications were innocuous.
James Clapper, the director of national intelligence under Mr Obama, on Sunday denied there was ever a FISA warrant relating to Trump Tower.
Democrats called Mr Trump's allegations against Mr Obama "ridiculous and unhinged". Chuck Schumer, leader of the Democrats in the Senate, said they were "beneath the dignity of the presidency".
Marco Rubio, a Republican senator on the Senate Intelligence Committee, said: "I have no insight into exactly what he (Mr Trump) is referring to. The president put that out there, and now the White House will have to answer for exactly what he was referring to."
"What I think we should do is, everybody needs to take a deep breath and calm down here."
Continuing his attacks on Mr Obama, the president said on Twitter: "Who was it that secretly said to Russian President 'Tell Vladimir that after the election I'll have more flexibility?'"
He appeared to be referring to a conversation, picked up on a microphone, between Mr Obama and then Russian president Dmitry Medvedev in March 2012.