The White House will not repeat again claims that British spies snooped on Donald Trump, Britain said Friday after the UK eavesdropping agency branded them "utterly ridiculous" in a rare public denial.
British Prime Minister Theresa May's spokesman reiterated the GCHQ agency's denial of a Fox News report -- which had been repeated by the US president's spokesman on Thursday -- and said the claims "should be ignored".
"We have made this clear to the administration and have received assurances that these allegations will not be repeated," the PM's spokesman said.
Britain's ambassador to Washington Kim Darroch and UK National Security Adviser Mark Lyall Grant spoke directly to the White House, the spokesman said, although he refused to specify whether the US administration had apologised.
The White House said Friday that Spicer had not accused Britain of spying on Trump but was "simply pointing to public reports, not endorsing any specific story".
May's spokesman pointed to the limits on employing intelligence capabilities imposed on Britain and the US -- along with Australia, Canada and New Zealand -- under the so-called "Five Eyes" pact.
The pact is an intelligence-sharing alliance forged from the embers of World War II.
"It's a situation that simply wouldn't arise," the spokesman said of the spying claims.
"We have a close, special relationship with the White House and that allows us to raise concerns as and when they arise as was true in this case," he added.
Late on Thursday, 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."
The press office of GCHQ -- the Government Communications Headquarters -- told AFP on Friday that it was "not unusual" for the agency to make public comment but acknowledged that "perhaps the tone of it was unusual".
The electronic eavesdropping agency does not normally comment on intelligence matters, though it has stepped up its public relations in recent months, including for recruitment drives and warnings on cyber-security.
- 'Get a grip' -
Trump had accused former US president Barack Obama on March 4 of a wiretapping plot that would almost certainly be against US law.
In a subsequent media report, Fox's legal analyst Napolitano claimed that "three intelligence sources have informed Fox News that president Obama went outside the chain of command" to order the surveillance.
"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," Napolitano said, claiming that Obama used Britain's GCHQ to circumvent US law.
Spicer repeated the allegations on Thursday, quoting from that Fox News report.
Members of Congress from both parties who are investigating the wiretapping allegations have found no evidence to support them.
Malcolm Rifkind, a former British foreign minister, said the White House should now make clear there was no evidence of any GCHQ involvement.
"That's just foolish and very, very dangerous stuff, and President Trump better get a grip," he told BBC radio.
"We're talking about the president of the US. You cannot have his official spokesman making allegations against a fellow NATO government.
"The White House needs to make it clear that they do not have, and have never had, any evidence that suggests that GCHQ or any British involvement in these matters was ever justified," he said.