The FBI and department of justice have been asked to hand over any evidence that Barack Obama wiretapped Donald Trump or his campaign, in a bid to get to the bottom of the president's explosive allegations.
Lindsey Graham, a Republican senator for South Carolina, and Sheldon Whitehouse, a Democrat senator for Rhode Island, jointly signed a letter yesterday addressed to both organisations, requesting clarification.
"The president has asked Congress to look into whether or not his campaign was wiretapped by the Obama administration," Mr Graham said, shortly after his letter was made public. "I will take up that challenge."
He continued: "The whole purpose of this is to see if a warrant was issued, directed at the Trump campaign."
Meanwhile, Mr Obama reportedly "rolled his eyes" when he saw Mr Trump's tweets accusing him of wiretapping.
Mr Obama believes his successor's claims "undermine the integrity of the office of the president", a source told NBC News.
However, Mr Obama did not believe his own integrity had been impugned because "he didn't do it".
Mr Graham and Mr Whitehouse have asked James Comey, the FBI director, and Dana Boente, the acting deputy attorney general, to respond.
Mr Boente is in charge of any potential investigation after Jeff Sessions, the attorney general, recused himself following revelations of a meeting with the Russian ambassador which he failed to disclose.
"We request that the department of justice provide us copies of any warrant applications and court orders - redacted as necessary to protect intelligence sources and methods that may be compromised by disclosure, and to protect any ongoing investigations," they wrote.
Mr Comey yesterday spoke at a cyber security conference in Boston, refusing to take questions and not discussing the specifics of wiretapping.
But the FBI director was reportedly "incredulous" about Mr Trump's accusations.
Mr Comey has reportedly asked the justice department to publicly refute Mr Trump's accusations - something it has yet to do.
But the White House has said Mr Trump does not accept Mr Comey's denial, and has called for an investigation. It would be illegal for the president to authorise a wiretap.
The White House struggled yesterday to answer whether it believes Mr Trump is the target of a counterintelligence investigation.
When first asked whether Mr Trump is the subject of such a probe, press secretary Sean Spicer said the White House needed to find that out.
"There's obviously a lot of concern," he said.
Mr Spicer added that the question is the reason why Mr Trump has asked Congress, specifically the House and Senate intelligence committees, to include the issue in its investigation into Russian involvement in the 2016 campaign.
Mr Spicer revised his response later in the briefing after an aide handed him a note.
"I just want to be really clear on one point, which is there is no reason that we have to think that the president is the target of any investigation, whatsoever," Mr Spicer said.
"There's no reason to believe that he is the target of any investigation. I think that's a very important point to make."
As the controversy rolled on, Mr Trump's administration was setting the stage for its healthcare reform.
Two Republican-controlled committees, the energy and commerce committee and the ways and means committee, yesterday examined the Bill, with a view to it moving to a full house vote next week.
But Republicans can only afford to lose two Republican votes in the Senate, and 22 in the House - assuming all Democrats vote against it.
Meanwhile Hawaii became the first US state to file a legal challenge to Mr Trump's revised travel ban, which restricts travel from six predominantly Muslim countries.
In a court filing, Hawaii said it would seek a temporary restraining order.
The state took similar action against Mr Trump's original and more sweeping executive order signed in January.
Legal arguments in the case are expected to be heard on March 15, a day before the new order is set to take effect. (© Daily Telegraph London)