Former MI6 officer Christopher Steele may be forced to reveal the sources behind the notorious 'dirty dossier' on Donald Trump

A former British spy may be forced to discuss the notorious 'dirty dossier' he wrote about Trump's alleged connections to Russia under oath.

US District Court Judge Ursula Ungaro issued a formal request for ex-MI6 officer Christopher Steele's testimony on Thursday.

Ungaro's ruling will allow Webzilla CEO Aleksej Gubarev to seek permission from British officials to question Steele about the funding and sourcing of the dossier.

The dossier, first published by Buzzfeed, alleged that Gubarev and his company were involved in 'altering operations against the Democratic Party leadership' during the 2016 election.

It claimed Russian agents had Gubarev steal data and send viruses in an attempt to help Donald Trump win the US election.

'His response is it is a lie. It is a fabrication. Never happened,' Valentin Gurvits, Gubarev's lawyer, told ABC News.

Buzzfeed eventually redacted Gubarev's name and the name of his company from the dossier, which was published on the website.

But Gubarev is still fighting to find out who Steele's sources are.

'My number one question is, "Why was this allegation about my clients included,'" Gurvitis said.

'Where did you get it? What did you do to verify it? And who did you communicate to?'

The ruling will allow Webzilla CEO Aleksej Gubarev (pictured) to seek permission from British officials to question Steele about the funding and sourcing of the dossier

The dirty dossier was brought to the FBI by John McCain after Steele, who worked as a spy in Moscow for 20 years after the collapse of the Soviet Union, shared his findings with the Republican senator.

Steele, 52, said in a British court filing that he wanted the dossier to be known to 'the United States governments at a high level by persons with responsibility for national security'.

McCain revealed that he delivered the 35-page document to the FBI because he could not asses on his own whether the controversial findings were real.

Glenn Simpson, the co-founder of Washington research firm Fusion GPS, is also being questioned next week.

Simpson, who hired Steele in the first place, will be interviewed by the Senate Judiciary Committee on August 22.

Among the dirty dossier's allegations was the claim that in 2013 Trump hired prostitutes to urinate on the bed of the Presidential Suite at the Moscow Ritz Carlton

Aides revealed that the committee plan to ask Simpson to reveal the clients who paid for dossier, but are reportedly 'not optimistic they will get an answer'.

Among the dirty dossier's allegations was the claim that in 2013 Trump hired prostitutes to urinate on the bed of the Presidential Suite at the Moscow Ritz Carlton, where he knew Barack and Michelle Obama had previously stayed.

It read: 'Trump's unorthodox behavior in Russia over the years had provided the authorities there with enough embarrassing material on the now Republican presidential candidate to be able to blackmail him if they so wished.'

Trump ridiculed the idea, pointing out that Russian hotel rooms are known to be rigged with cameras and describing himself as a 'germophobe'.