The White House has assured the Government that allegations that British intelligence services spied on Donald Trump will not be repeated, Prime Minister Theresa May's official spokesman has said.
GCHQ described as "utterly ridiculous" the claims, repeated by the US president's official spokesman, that the eavesdropping agency was used by Barack Obama to spy on Mr Trump before last year's election.
The Government then "made clear" to the US that the "ridiculous" claims should be ignored and received assurances in return that they will not be repeated, showing that the administration does not give them any credence, Mrs May's spokesman said.
The PM's spokesman said it would not be possible for GCHQ to spy on Mr Trump as both countries are members of the Five Eyes alliance, a joint intelligence co-operation agreement which also includes Australia, Canada and New Zealand.
"I would add, just as a matter of fact, with the Five Eyes pact, we cannot use each other's capabilities to circumvent laws," he said.
"It's a situation that simply wouldn't arise."
During a media briefing at the White House on Thursday, presidential spokesman Sean Spicer drew reporters' attention to comments made earlier this week on Fox News by former judge Andrew Napolitano in relation to Mr Trump's controversial claim that his New York residence had been bugged.
Detailing a long list of reports about the wiretap claims, Mr Spicer quoted Mr Napolitano as saying: "Three intelligence sources have informed Fox News that President Obama went outside the chain of command - he didn't use the NSA, he didn't use the CIA, he didn't use the FBI and he didn't use the Department of Justice - he used GCHQ."
In a surprise break from its normal practice of refusing to comment on allegations about its activities, GCHQ released a statement on Thursday night, saying: "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."
Mr Spicer's intervention came shortly after the US Senate Intelligence Committee released a statement saying they had seen no evidence to support the US president's claim - made in a series of Twitter posts earlier this month - that Mr Obama had bugged Trump Towers.
In a statement, the committee's Republican chairman Richard Burr and his Democrat counterpart Mark Warner said: "Based on the information available to us, we see no indications that Trump Tower was the subject of surveillance by any element of the United States government either before or after Election Day 2016."