Donald Trump remained unrepentant amid a diplomatic row with Britain on Friday, hours after US officials made a formal apology for accusing GCHQ of helping Barack Obama spy on the then presidential candidate.

Sean Spicer, the president's press secretary, repeated a claim on Thursday evening – initially made by an analyst on Fox News – that GCHQ was used by Mr Obama to spy on Trump Tower in the lead-up to last November's election.

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."