Christopher Steele has been the subject of more than 50 tweets by President Trump

The former MI6 agent behind the Trump dossier has agreed to be questioned by US officials over his relationship with the FBI.

Christopher Steele, 54, has agreed to meet investigators in London within weeks, according to a source close to him. Mr Trump has tweeted more than 50 times about Mr Steele, calling him a “failed spy” and accusing him of spreading fake news.

Last year Mr Steele, who runs a corporate intelligence company, was named as the author of memos containing unsubstantiated allegations that the Kremlin held sexually lurid information about Mr Trump.

Mr Steele’s dossier led to an FBI inquiry, which became a two-year investigation presided over by the special counsel Robert Mueller. That found that figures in the Trump campaign team expected