A Republican-chaired intelligence committee has asked the Trump administration for evidence to back up the US President's claim Barack Obama had "wires tapped" at Trump Tower during last year's presidential campaign.

President Donald Trump asserted in a tweet earlier this month: "Terrible! Just found out that Obama had my 'wires tapped' in Trump Tower just before the victory. Nothing found. This is McCarthyism!"

He continued the allegation against the former president in other tweets but offered no evidence.

Loading

The request for evidence was made in a letter sent by the chairman of the House Intelligence Committee, Republican representative Devin Nunes, and the panel's ranking Democrat, representative Adam Schiff, according to a congressional aide, who requested anonymity.

Mr Obama's director of national intelligence, James Clapper, said nothing matching Mr Trump's claims had taken place, but that has not quelled speculation Mr Trump's communications were monitored by the Obama administration.

Mr Trump has asked Congress to investigate.

Early last week, Mr Schiff said the committee would answer the President's call to investigate the claim.

He said he would also ask FBI Director James Comey directly when he appears later this month before the full committee, which is investigating Russian activities during the election.

"We should be able to determine in fairly short order whether this allegation is true or false," Mr Schiff said.

Mr Nunes said so far he had not seen any evidence to back up Mr Trump's claim and suggested the news media were taking the President's tweets too literally.

"The President is a neophyte to politics — he's been doing this a little over a year," Mr Nunes said.

Other lawmakers have asked for similar evidence.

Declaring that Congress "must get to the bottom" of Mr Trump's claim, Republican senator Lindsey Graham and Democrat senator Sheldon Whitehouse asked Mr Comey and Acting Deputy Attorney-General Dana Boente to produce the paper trail created when the Justice Department's criminal division secures warrants for wire-taps.

Rebukes from both sides after accusation

Mr Trump last month spoke fondly of his relationship with Mr Obama. (file photo) ( AP: Pablo Martinez Monsivais )

Mr Trump's wire-tapping claims drew bipartisan rebukes from Democrats and Republicans alike, who find his habit of venting on social media to be beneath the office of the President.

Representative Eric Swalwell, a Democrat who is a member of the House Intelligence Committee, downplayed Mr Trump's allegation, saying: "I think this is just the President up early doing his routine tweeting."

"Presidents don't wire tap anyone. These are pursued by the Department of Justice in accordance with the FBI and signed off by a judge."

Loading

Still, the morning tweets stood out given the gravity of the charge and the strikingly personal attack on the former president. Mr Trump as recently as last month spoke fondly of his relationship with Mr Obama, despite their differences.

Mr Schiff called Mr Trump's assertion a "spectacularly reckless allegation".

"If there is something bad or sick going on, it is the willingness of the nation's chief executive to make the most outlandish and destructive claims without providing a scintilla of evidence to support them," he said.

AP/Reuters