A former aide to Donald Trump "substantially hindered" FBI efforts to question a mysterious professor who used to work for Stirling University, US court documents allege.

George Papadopoulos is accused of initially lying to US authorities about his links with Professor Joseph Mifsud.

Prof Mifsud, a Maltese academic who worked for Stirling, is said to have set up a number of meetings between Papadopoulos and Russian officials.

A US criminal indictment last year quoted a number of emails and summarises verbal communications in 2016 between the Trump aide and an anonymous professor, who was later identified as Prof Mifsud.

Prof Mifsud has now been named in a sentencing memo filed by prosecutors.

The interactions between the pair include Prof Mifsud allegedly informing Papadopoulos of "dirt" on Hillary Clinton, an accusation he denies.

They occurred several months before an enormous tranche of Democratic National Committee (DNC) emails were released by Wikileaks following server breaches by suspected Russian hackers in July 2015 and April 2016.

Papadopoulos has pleaded guilty to wilfully misleading FBI agents about his relationship with the professor.

The indictment against him alleges Prof Mifsud put him in contact with a man who had links to Russia's ministry of foreign affairs.

Prof Mifsud also allegedly arranged a meeting in London where he introduced a Russian woman to Papadopoulos, falsely claiming she was President Putin's niece.

The new sentencing memo in Papadopoulos' case was issued on Friday by prosecutors working for US special counsel Robert Mueller, who is investigating possible ties between the Trump campaign and Moscow.

It claims Papadopoulos' alleged lies "impeded the FBI's investigation into Russian interference in the 2016 presidential election".

The court filings continue: "Most immediately, those statements substantially hindered investigators' ability to effectively question (Prof Mifsud) when the FBI located him in Washington DC approximately two weeks after the defendant's January 27, 2017, interview.

"The defendant's lies undermined investigators' ability to challenge the professor or potentially detain or arrest him while he was still in the United States.

"The government understands that the professor left the United States on February 11, 2017, and he has not returned to the United States since then."

The documents go on to describe an interview between Papadopoulos and FBI agents in which he "repeatedly and falsely claimed that his interactions with the professor occurred before he was working for the Trump campaign".

The suggestion Prof Mifsud had told the then-Trump adviser of the Russians possessing "dirt" on Clinton was not at first mentioned and "only came up after additional specific questioning from the agents", the memo adds.

It concludes: "Had the defendant told the FBI the truth when he was interviewed in January 2017, the FBI could have quickly taken numerous investigative steps to help determine, for example, how and where the professor obtained the information, why the professor provided the information to the defendant, and what the defendant did with the information after receiving it."

Mueller is recommending a jail sentence for Papadopoulos of up to six months.

Prof Mifsud quit his post at Stirling in November last year in the wake of the Papadopoulos indictment's revelations.

In media interviews shortly after the story first broke, the academic protested his innocence, saying that while he helped Papadopoulos network with contacts, he had nothing to do with "dirt".

"I never got a penny from the Russians, my conscience is clean," he told an Italian newspaper.

Prof Mifsud's present whereabouts are unknown, with CNN reporting on November 10 that he had "disappeared" from another university in Rome where he also teaches.

Buzzfeed reported in February that he cut contact with his pregnant Ukrainian fiancee following the revelations.

Another recent Buzzfeed story found that Prof Mifsud had failed to show up at a Sicilian court on charges of financial wrongdoing at a university in 2010.

As STV News revealed last year, at the time of his interactions with Papodopoulos in the spring of 2016, Prof Mifsud was working for Stirling University as a part-time professorial teaching fellow.

Emails obtained by STV also showed that university management had boasted to staff in the politics department of the academic's links to Vladimir Putin, around the same time as his meetings with the Trump aide.

Questions have been raised about Prof Mifsud's activities in the UK, where he became director of the now-defunct London Academy of Diplomacy in 2012 and was involved with the University of East Anglia as well as Stirling.

The Scottish university claimed the academic was hired due to his "portfolio... (in) international affairs and diplomacy, reflecting his academic and professional background in this field".

There is no evidence of any academic research carried out in these fields by Prof Mifsud, whose academic background is in education.

Stirling University refused an information request from STV News for details of Prof Mifsud's academic background in international affairs and diplomacy, citing data protection.

He did serve as a private secretary to former Maltese foreign minister Michael Frendo between 2006 and 2007 but does not ever appear to have been a formal diplomat.

Prof Mifsud was also pictured with Boris Johnson while he was still British foreign secretary at a fundraising dinner in Berkshire last October.

Former UK culture secretary Ben Bradshaw has written twice to Stirling principal Professor Gerry McCormac seeking further clarity on Prof Mifsud's role at the institution.

The Labour MP wanted to know more about the university's involvement with the academic, including the history of his connections with both Prof McCormac and Stirling's ex-deputy principal Professor John Gardner.

He further asked about Stirling's involvement with the institution Prof Mifsud ran from 2012 until its closure in 2016, the London Academy of Diplomacy.

The diplomatic school partnered with Stirling in 2014, around the same time it had reported annual financial losses of nearly £4m - and "administrative expenses" of £7.5m.

Bradshaw has criticised both Stirling and the University of East Anglia for a "lack of transparency" over their dealings with the Maltese professor and the academy

The MP branded his last reply from Prof McCormac as "wholly unsatisfactory", adding: "It doesn't begin to answer any of my substantive questions."