A dossier of embarrassing allegations about Donald Trump produced by a former British spy "probably" has "some credibility", the ex-head of MI6 has said.

Christopher Steele, himself a former MI6 officer, compiled the dossier in which he claimed Russia held compromising information on the US president which left him vulnerable to blackmail.

At the time, Mr Trump denounced the document as fake news, and its veracity has widely been questioned.

But Sir Richard Dearlove, who ran MI6 between 1999 and 2004, told BBC's Newsnight programme: "I think that there is probably some credibility to the content.. I wouldn't put it any more forcefully than that."

Among the more lurid allegations was a claim that the Russians held evidence of Mr Trump hiring prostitutes during a visit to Moscow to urinate on a hotel bed which he believed Barack and Michelle Obama had previously slept in.

The file also claimed that the Trump campaign team had multiple contacts with Russian officials during the presidential election race.