The publication of a controversial dossier about President Donald Trump's alleged links with Russia, authored by a former MI6 spy, has already resulted in a death, it has been claimed.

Glenn Simpson the co-founder of Fusion GPS, the firm which commissioned the dossier written by Christopher Steele, was giving evidence to a congressional committee during a closed-door interview last year.

A transcript of his testimony was released by the top Democrat on the Senate Judiciary Committee, Dianne Feinstein, on Tuesday, who said making it public would "set the record straight".

Quizzed on whether he had taken any steps to assess the credibility of Mr Steele's sources, Mr Simpson declined to comment.

Coming to his defence, his lawyer Joshua Levy said it was a "voluntary interview", and stated that he "wants to be very careful to protect his sources".

He added: "Somebody's already been killed as a result of the publication of this dossier and no harm should come to anybody related to this honest work."

The emergence of the dossier - containing a series of lurid claims that the Russians had gathered compromising material on the president prior to his election campaign - caused outrage in the Trump camp.

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

During hours of questioning, Mr Simpson also revealed Mr Steele took the dossier to the FBI in July 2016, and said his concern was "whether or not there was blackmail going on, whether a political candidate was being blackmailed or had been compromised".

He also divulged that the FBI believed Mr Steele's information might be credible "because they had other intelligence that indicated the same thing and one of those pieces of intelligence was a human source from inside the Trump organisation".

When asked who that source may have been an answer was declined on the basis of "security", with Mr Simpson adding that "people who get in the way of the Russians tend to get hurt".

The dossier was reportedly the result of an investigation initially funded by Republicans who were seeking to block Mr Trump from becoming the party's presidential candidate, before being taken over by Democrats after his nomination.

Mr Steele was said to have passed on his findings to both US and UK intelligence in the run-up to the 2016 presidential election due to concerns about national security for both countries.

Mr Trump has derided the dossier as politically motivated, and several Republican-led committees are investigating whether it formed the basis for the FBI's initial investigation into Russian election interference.

Democrats say those investigations are a distraction.

The transcript reveals Mr Simpson also told the committee that Mr Steele was the "lead Russianist at MI6 prior to leaving" and was someone he had worked with since 2009.

He said Mr Steele was someone who "delivered quality work in very appropriate ways" who had a "sterling reputation", and who "doesn't exaggerate, doesn't make things up, doesn't sell baloney".

Earlier this month two senior Republican senators referred Mr Steele, over statements about the "distribution of claims contained in the dossier", to the US Department of Justice (DoJ) - urging them to investigate him.

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

At the time RPC, the UK law firm representing Mr Steele, declined to comment.