Christopher Steele, the former MI6 officer who attracted Donald Trump’s fury for drafting a dossier of allegations about collusion with Moscow, was involved in efforts to flip a high-profile Russian oligarch, according to newly released emails.

They reportedly reveal that the British agent helped American officials target Oleg Deripaska, a Kremlin-linked billionaire, as part of an effort to persuade influential figures to pass on information about any assistance given to Mr Trump’s election campaign.

The details were revealed in emails obtained by The New York Times, which said they had been passed from the Department of Justice to Republicans in Congress.

They will be seized on by Mr Trump’s allies as further evidence that Mr Steele – a frequent target of their attacks – was part of a “deep state” conspiracy to bring down the president.

The president himself spent part of a holiday weekend quoting approvingly from a conservative column that accused Mr Steele of trying to “verify the unverifiable”.