The whistleblower accusing President Donald Trump of abuse of power worked with Joe Biden when he was vice president, according to a new report.

On Wednesday, attorneys for the CIA whistleblower issued a carefully-worded statement denying that the had a 'professional' link to a 2020 Democratic candidate, saying he is an apolitical civil servant.

Now an intelligence source says that it is likely that the unnamed CIA analyst, who is clearly an expert on Ukraine issues, briefed Biden and probably even accompanied him on Air Force Two on one or more of Biden's six visits to the country.

'From everything we know about the whistleblower and his work in the executive branch then, there is absolutely no doubt he would have been working with Biden when he was vice president,' a retired CIA officer told the Washington Examiner.

The Biden campaign did not immediately respond to a request for comment from DailyMail.com on Thursday evening.

Biden is seen with then-President Barack Obama signing executive orders to close down the detention center at Guantanamo Bay Cuba in 2009. Source say that Biden worked closely with the CIA whistleblower while serving as vice president

Trump has accused the whistleblower of having ties to one of his political opponents

Separately, a former Trump administration official told the Examiner that Biden’s work on foreign affairs as vice president brought him into close proximity with the whistleblower.

“This person, after working with Biden, may feel defensive towards him because he feels [Biden] is being falsely attacked. Maybe he is even talking to Biden’s staff,” the former official said. “Maybe it is innocent, maybe not.”

The whistleblower's alleged political bias has become the subject of various accusations following a report that the Intelligence Community Inspector General said that the person 'worked or had some type of professional relationship with one of the Democratic candidates.'

The claim of a 'professional link' between the CIA agent and a candidate was first made in an article by Washington Examiner columnist and conservative commentator Byron York.

The whistleblower, who alleges misconduct on Trump's part, had already been identified as having a Democratic party affiliation.

A person with knowledge of the Inspector General (IG) for the Intelligence Community's recent testimony to the House, was reported by York to have indicated there was an additional 'professional relationship.'

'The IG said [the whistleblower] worked or had some type of professional relationship with one of the Democratic candidates,' a source told the Examiner.

Another source told the paper: 'The IG said the whistleblower had a professional relationship with one of the 2020 candidates.'

After Trump tweeted a link to the Examiner report, the unnamed CIA agent's attorneys issued a rare public statement claiming that there was a 'professional relationship' between the whistleblower and a candidate.

Trump tweeted: 'This is just the beginning.' Later on Tuesday he tweeted: 'The Whistleblower has ties to one of my DEMOCRAT OPPONENTS.'

But late Wednesday, the lawyers said they wanted to 'clarify some facts,' and said in the statement: 'Our client has never worked for or advised a political candidate, campaign, or party.

'Second, our client has spent their entire government career in apolitical, civil servant positions in the Executive Branch.

'Third, in these positions our client has come into contact with presidential candidates from both parties in their roles as elected officials – not as candidates.'

Rare statement: How the whistleblower's attorneys slapped back at the president

The whisteblower's attorneys - who did not confirm that the official is a male CIA agent, although that aspect of his identity is already known - went on to slam suggestions that his complaint was not credible and said he had told the inspector general about his career to help establish its credibility.

'Fourth, the whistleblower voluntarily provided relevant career information to the ICIG in order to facilitate an assessment of the credibility of the complaint,' the attorneys said.

'Fifth, as a result, the ICIG concluded – as is well known – that the complaint was both urgent and credible.

Finally, the whistleblower is not the story. To date, virtually every substantive allegation has been confirmed by other sources. For that reason the identity of the whistleblower is irrelevant.'

The combination of a clapback at the president by the attorneys, and a hint of more information about the official's resume, will only add to the drama surrounding the complaint.

Pointedly, the lawyers called their client 'whisteblower #1,' a reference to a report that they have another or possibly even multiple other whistleblowers who are in the process of making complaints.

The IG, Michael Atkinson, had provided vague information in a letter to the House Intelligence Committee in August, writing the whistle-blower had 'some indicia of an arguable political bias ... in favor of a rival political candidate.'

The whistle-blower in a complaint alleges that Trump asked the President of Ukraine to investigate the Bidens to help his own 2020 reelection. An unsealed call shows Trump bringing up the Bidens with the Ukrainian president.

Who could it be? Amy Klobuchar, Cory Booker, Pete Buttigieg, Bernie Sanders, Joe Biden, Elizabeth Warren, Kamala Harris, Andrew Yang, Beto O'Rourke and Julian Castro Third 2020 Democratic Party Presidential Debate, Houston, USA. A report connected the whistle-blower to one of the 2020 candidates

The president has previously gone after the whistle-blower, identified by the New York Times as a CIA officer who has been detailed to the White House at some point, and demanded the right to face his accuser.

The Washington Post reported that House Democrats may interview the whistle-blower at an off-site location to protect their identity, amid concerns it could leak.

In remarks caught on video, Trump said: 'I want to know who's the person, who's the person who gave the whistle-blower the information? Because that's close to a spy.' He continued: 'You know what we used to do in the old days when we were smart? Right? The spies and treason, we used to handle it a little differently than we do now,' he said, referencing execution.

A group of 90 national security professionals has applauded an unidentified whistle-blower.

'While the identity of the whistleblower is not publicly known, we do know that he or she is an employee of the U.S. Government. As such, he or she has by law the right—and indeed the responsibility—to make known, through appropriate channels, indications of serious wrongdoing,' the officials wrote.

'That is precisely what this whistleblower did; and we applaud the whistleblower not only for living up to that responsibility but also for using precisely the channels made available by federal law for raising such concerns,' said the security officials, who served Democratic and Republican presidents.