The comments prompted a furious response from GCHQ, which in a break from normal practice issued a public statement: “Recent allegations made by media commentator Judge Andrew Napolitano about GCHQ being asked to conduct ‘wiretapping’ against the then president-elect are nonsense. They are utterly ridiculous and should be ignored.”

Intelligence sources told The Telegraph that both Mr Spicer and General McMaster, the US National Security Adviser, have apologised over the claims. “The apology came direct from them,” a source said.

Mr Spicer had earlier repeated claims that Barack Obama used GCHQ to spy on Mr Trump before he became president.

“He’s able to get it and there’s no American fingerprints on it,” Mr Spicer said of the intelligence supposedly provided to Mr Obama by Britain.