Britain's intelligence and security organisation has dismissed claims, suggested by the White House, that it helped Barack Obama spy on Donald Trump as "nonsense" in an incredibly rare public statement.

Sean Spicer, Mr Trump'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.

In a break from its normal practice of refusing to comment on allegations about its activities, a spokesman for GCHQ said: "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."