The former MI6 spy behind the dirty dossier that accused Donald Trump of asking prostitutes to urinate on a hotel bed because Barack Obama once slept there has insisted his report is '70-90% accurate'.

Christopher Steele told friends that his dossier will be vindicated by the ongoing special investigation into Trump's links with Russia, according to a new book.

'I've been dealing with this country for thirty years. Why would I invent this stuff?,' Steele is quoted as saying in Guardian journalist Luke Harding's book titled Collusion: How Russia Helped Trump Win.

Christopher Steele told friends that his report will be vindicated by the ongoing special investigation into Trump's links with Russia, according to a new book

Friends said Steele admitted that intelligence is rarely 100 per cent correct but said that most of his information was 'proven up' and his sources were reliable, according to the book.

Steele's 35-page dossier claims that Russia collected a file of compromising information on Trump including sex tapes with which to blackmail him.

It also claims that Trump was cultivated and supported by Russia for five years before he was elected and that his contacts met with Kremlin representatives.

The dossier was published by Buzzfeed on 10 January 2017 after several media outlets refused to because they could not verify the claims.

Harding claims that the dossier was taken seriously by US investigators because of Steele's reputation.

He wrote more than a hundred reports on Russia and Ukraine and his investigation into soccer organisation FIFA led to seven arrests.

Harding writes: 'The episode burnished Steele's reputation inside the US intelligence community and the FBI. Here was a pro, a well-connected Brit, who understood Russian espionage and its subterranean tricks. Steele was regarded as credible.'

Steele, 53, allegedly told friends he was shocked by the extent of alleged collusion between Trump and Russians.

'For anyone who reads it, this is a life-changing experience,' he told them, according to the book.

But as the November 2016 election loomed, Steele allegedly told friends that his FBI sources were drying up as they insisted he could not go public with material involving a presidential candidate.

Steele said he felt he was in possession of a 'radioactive hot potato'.

Trump (pictured on the White House lawn on Tuesday) denied the allegations made in the report, branding it 'fake news'

The claim by Steele's friends that he insists his report is largely true is the first we've heard from the former spy, who runs a private intelligence firm Orbis, since it was published.

Last month the chairman of the Senate Intelligence committee pleaded with Steele to come and talk to U.S. investigators to disclose sources and funders of the infamous dirty dossier - but he refused.

Senate Intelligence Committee Chairman Richard Burr brought up the dossier, unprompted, during a status update on the panel's nine-month probe into Russian interference in the presidential election.

He indicated that he had personally implored the former British Intelligence officer to come talk to him – even on a basis where Steele could speak exclusively to the two panel leaders without a compliment of prying lawmakers or aides.

'As it relates to the Steele dossier, Burr said, 'unfortunately, the committee has hit a wall.'

'We have on several occasions made attempts to contact Mr. Steele. To meet with Mr. Steele. To include personally the vice chairman and myself as two individuals making that connection. Those offers have gone unaccepted,' Burr vented, with Warner at his side.

Part of the document is seen above. Click here to see the full document first published by Buzzfeed

The panel continues to probe possible collusion with the Trump campaign, but has reached no conclusions.

'The committee continues to look into all evidence to see if there was any hint of collusion,' Burr said. 'We have more work to do as it relates to collusion.'

Special counsel Robert Mueller is also probing the dossier, having taken over an FBI investigation into the document.

Of interest are its findings on Trump and his associates' financial links to Russia. The dossier mentions Russian businessmen who U.S. intelligence concluded are Russian intelligence officers, according to the report.

Trump denied the allegations made in the report, branding it 'fake news'.