Donald Trump's decision to declassify evidence given by ex-British spy Christopher Steele over the former president's alleged links with Russia led to the disappearance of two sources, Steele said.

Steele said in a witness statement that Trump’s decision to declassify his 2017 testimony to Special Counsel Robert Mueller’s investigation was “one of the most egregious breaches of intelligence rules and protocol by the US government in recent times”.

The former intelligence officer also said: “Two of the named Russian sources have not been seen or heard of since.”

His witness statement was made public on Tuesday, the day after Trump asked London’s High Court to allow his data protection lawsuit against a British private investigations firm co-founded by Steele to continue.