An American academic who met with the President's advisers in 2016 could have been an FBI informant for its probe into the Trump campaign’s alleged collusion with Russian, reports suggest.

Both the Times and Washington Post have reported that the FBI made use of a US-born academic working in the UK as an informant, and that he met with Carter Page and George Papadopoulos, two Trump aides suspected of dealing with the Russians.

This came after the Daily Caller reported that both Page and Papadopoulos met in 2016 with an American professor at Cambridge University, which it named as Stefan Halper. He asked several questions about Russia which prompted suspicions.

Following the reports and naming of the professor, Trump tweeted: 'If the FBI or DOJ was infiltrating a campaign for the benefit of another campaign, that is a really big deal.

'Only the release or review of documents that the House Intelligence Committee (also, Senate Judiciary) is asking for can give the conclusive answers. Drain the Swamp!'

Stefan Halper is a Cambridge Academic and has been named in several reports as an FBI informant on the Trump campaign. He is pictured in an undated image speaking at the Oxford Union debating society

Talk of an alleged informant has angered President Trump, who is pictured speaking at a round table event in Washington on May 16

Following the reports and naming of the professor, Trump tweeted: 'If the FBI or DOJ was infiltrating a campaign for the benefit of another campaign, that is a really big deal'

Papadopoulos revealed in a plea agreement to having been told by an apparent Russian agent that the Putin government had access to a raft of hacked Hillary Clinton emails before this was made public. He has since pleaded guilty to lying to the FBI.

Page, meanwhile, was under surveillance by the FBI at the time he met with Professor Halper, who had links to both the CIA and MI6.

Papadopoulos first met Halper after the academic invited him to England in September 2016 to discuss energy issues, two sources familiar with his account told NBC News.

The Trump aide found Halper's behavior during these meetings suspicious, the sources said, and also noticed that the academic’s young assistant appeared to flirt with him both during and after the exchanges.

Papadopoulos said Halper, who is now retired, randomly brought up Russians and Clinton's emails, adding to his suspicions.

Page told the Daily Caller he met with Halper several times, including on the academic's farm in Virginia. However, Page told NBC he did not find these encounters concerning.

Halper also met with a third Trump campaign official, to whom he reportedly expressed interest in helping the president's campaign.

There is no public evidence that Halper was an FBI informant, and official sources have refused to comment on the subject. Halper has not given any comment on the issue.

George Papadopoulos was one of three Trump aides that met with Professor Halper during 2016

Carter Page, a Trump adviser who was under FBI surveillance before the 2016 election. He is pictured on December 12, 2016, in Moscow

The academic has long-established connections to both British and American intelligence services.

He worked closely with former MI6 chief Sir Richard Dearlove at the Cambridge Security Initiative, an intelligence consulting group.

Meanwhile, his father-in-law was Ray Cline, who served as director of the CIA's bureau of intelligence and research. Halper also worked with a team of former CIA officials on George H.W. Bush's failed presidential bid.

Allegations that the FBI planted an informant in the Trump campaign have angered the President.

In a series of late night calls to allies, including Meadows and Fox News anchor Sean Hannity, Trump has used the reports as evidence that the so-called deep state of career government officials has been working against him.

The President thrust the issue into the limelight with a tweet on Friday.

He quoted Fox News anchor David Asman, who said: 'Apparently the DOJ put a Spy in the Trump Campaign. This has never been done before and [is not] by any means necessary, they are out to frame Donald Trump for crimes he didn't commit'.

Trump has frequently fumed about the Russia probe even while in White House meetings this week about other topics, according to a White House official.

Trump's lawyer, Rudy Giuliani, told CNN on Friday neither he or Trump actually knew for sure if there was an informant or not

Trump tweeted a quote from Fox News anchor David Asman, claiming the DOJ would 'frame him for crimes he didn't commit'

Talk of the reported FBI source has rocketed through the conservative media, with several people putting forward Halper as the likely suspect.

Hannity discussed the issue on his show Wednesday - and was a centerpiece of Giuliani's attacks on the probe Friday.

'I want to know because I believe, if there was an embedded person, that person cleared us because the FBI cleared us.

‘I wonder what the heck is the legitimacy of the Mueller investigation in the first place,' Giuliani told CNN.

Trump allies have increasingly pushed for ways to paint Mueller and his investigators as political actors in an effort to discredit his findings or justify his possible dismissal.

They have painted the informant as a 'spy', although this suggests an agent permanently embedded within the campaign, an impression the FBI would refute.

A number of Trump outside advisers - including former chief strategist Stephen Bannon - have stepped up their attacks on the Department of Justice, calling for it to release more documents to the White House while saying a confidential source has worked against Trump.

Working from his Capitol Hill town house, Bannon has consulted with Trump-friendly congressmen including Nunes and Rep. Mark Meadows, to rally support among Republicans and push Trump to act more aggressively, according to two people familiar with the discussions but not authorized to discuss them publicly.'