US politicians are calling for a probe into the British former MI6 officer behind a ‘dirty dossier’ about Trump’s alleged links with Russia.

Christopher Steele has been referred to the Department of Justice by two Republican senators over the report, which accused Trump of asking prostitutes to urinate on a hotel bed where Obama once slept.

Senate judiciary committee chairman Chuck Grassley and Lindsey Graham said they had passed a classified memo to the DoJ relating to communications between Mr Steele and “multiple US news outlets”.

The 35-page dossier claimed the Russians had compromising material on Trump prior to his election campaign.

Mr Steele, who runs London- based Orbis Business Intelligence, was temporarily in hiding when he was identified as the author.

The most eye-catching claim was that in 2013 Trump hired prostitutes to urinate on the bed of the Presidential Suite at the Moscow Ritz Carlton, as he knew Barack and Michelle Obama had previously stayed there.

The report states: "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 slammed the claims as "fake news" when they were published by Buzzfeed in January.

However, former head of MI6 Richard Dearlove recently said that the claims had "some credibility".

Steele is reported to have broken his silence on the claims in a new book by Guardian journalist Luke Harding.

He is quoted as saying: “I’ve been dealing with this country for thirty years. Why would I invent this stuff?"

The book claims the reports have been taken seriously in Washington due to Steele's reputation for producing reliable reports on Russia.

The dossier is being probed as part of an investigation by special counsel Robert Mueller probing alleged collusion between Trump and Russia in the run-up to the 2016 US Presidential election.

Last month, the chairman of the Senate Intelligence committee pleaded with Steele to come and talk to U.S. investigators about the dossier.

The British spy has so far declined a number of invitations.

Responding to the accusations earlier this year, Trump said: "It's phony news by sick people.

"I’m surrounded by bodyguards, surrounded by people, I always tell them... In your hotel rooms and wherever you go you’re going to probably have cameras.

"In those rooms you have cameras in the strangest places... You’d better be careful or you’ll be watching yourself on nightly TV. I tell this to people all the time.

"I’m also very much of a germaphobe by the way."