WASHINGTON — President Trump refused to back down on Friday after his White House aired an unverified claim that Britain’s spy agency secretly monitored him during last year’s campaign at the behest of President Barack Obama.
Although his aides in private conversations since Thursday night had tried to calm British officials who were livid over the claim, Mr. Trump made clear that he felt the White House had nothing to retract or apologize for. He said his spokesman was simply repeating an assertion made by a Fox News commentator.
“We said nothing,” Mr. Trump told a German reporter who asked about the matter at a joint White House news conference with Chancellor Angela Merkel. “All we did was quote a certain very talented legal mind who was the one responsible for saying that on television. I didn’t make an opinion on it.” He added: “You shouldn’t be talking to me. You should be talking to Fox.”
Mr. Trump, who has stuck by his unsubstantiated assertion that Mr. Obama ordered his telephone tapped last year despite across-the-board denials, wryly used Ms. Merkel’s visit to repeat his contention. Ms. Merkel was angry during Mr. Obama’s administration at reports that the United States had tapped her cellphone and those of other foreign leaders. Turning to her, Mr. Trump said, “At least we have something in common, perhaps.”
After the news conference Mr. Spicer echoed Mr. Trump’s defiant tone. “I don’t think we regret anything,” he told reporters. “As the president said, I was just reading off media reports.”
Shortly afterward, Fox backed off the claim made by its commentator, Andrew Napolitano. “Fox News cannot confirm Judge Napolitano’s commentary,” the anchor Shepard Smith said on air. “Fox News knows of no evidence of any kind that the now president of the United States was surveilled at any time, any way. Full stop.”
A spokesman for Prime Minister Theresa May of Britain said on Friday that the White House had backed off the allegation. “We’ve made clear to the administration that these claims are ridiculous and should be ignored,” the spokesman said, on the condition of anonymity in keeping with British protocol. “We’ve received assurances these allegations won’t be repeated.”
Kim Darroch, the British ambassador to Washington, spoke with Sean Spicer, the White House press secretary, at a St. Patrick’s Day reception in Washington on Thursday night just hours after Mr. Spicer aired the assertion at his daily briefing. Mark Lyall Grant, the prime minister’s national security adviser, spoke separately with his American counterpart, Lt. Gen. H.R. McMaster.
“Ambassador Kim Darroch and Sir Mark Lyall expressed their concerns to Sean Spicer and General McMaster,” a White House official said on the condition of anonymity to confirm private conversations. “Mr. Spicer and General McMaster explained that Mr. Spicer was simply pointing to public reports, not endorsing any specific story.”
Other White House officials, who also requested anonymity, said Mr. Spicer had offered no regret to the ambassador. “He didn’t apologize, no way, no how,” said a senior West Wing official. The officials said they did not know whether General McMaster had apologized.
The controversy over Mr. Trump’s two-week-old unsubstantiated accusation that Mr. Obama had wiretapped his telephones last year continued to unnerve even fellow Republicans. Representative Tom Cole of Oklahoma said on Friday that Mr. Trump had not proven his case and should apologize to Mr. Obama.
“Frankly, unless you can produce some pretty compelling truth, I think President Obama is owed an apology,” Mr. Cole told reporters. “If he didn’t do it, we shouldn’t be reckless in accusations that he did.”
The flap with Britain started when Mr. Spicer, in the course of defending Mr. Trump’s original accusation against Mr. Obama, on Thursday read from the White House lectern comments by Mr. Napolitano asserting that the British spy agency was involved. Mr. Napolitano said on air that Mr. Obama had used Britain’s Government Communications Headquarters, the signals agency known as the GCHQ, to spy on Mr. Trump.
The GCHQ quickly and vehemently denied the contention on Thursday in a rare statement issued by the spy agency, calling the assertions “nonsense” and “utterly ridiculous.” By Friday morning, Mr. Spicer’s briefing had turned into a full-blown international incident. British politicians expressed outrage and demanded apologies and retractions from the American government.
Mr. Trump’s critics assailed the White House for alienating America’s ally. “The cost of falsely blaming our closest ally for something this consequential cannot be overstated,” Susan E. Rice, who was Mr. Obama’s national security adviser, wrote on Twitter. “And from the PODIUM.”
Mr. Trump has continued to stick by his claim about Mr. Obama even after it has been refuted by a host of current and former officials, including leaders of his own party. Mr. Obama denied it, as did the former director of national intelligence. The F.B.I. director has privately told other officials that it is false. After being briefed by intelligence officials, the Republican chairmen of the House and Senate Intelligence Committees have in the last few days said they have seen no indication that Mr. Trump’s claim is true.
Mr. Spicer tried to turn the tables on those statements during his briefing on Thursday by reading from a sheaf of news accounts that he suggested backed up the president. Most of the news accounts, however, did not verify the president’s assertion, while several have been refuted by intelligence officials.
For instance, Mr. Spicer read several articles from The New York Times, which has written extensively on an investigation into contacts between associates of Mr. Trump and Russian officials. The Times has reported that intelligence agencies have access to intercepted conversations as part of that investigation. But it has never reported that Mr. Obama authorized the surveillance, nor that Mr. Trump himself was monitored.
Representative Devin Nunes of California, a Republican and the chairman of the House Intelligence Committee, said this week that “it’s possible” that Mr. Trump or others were swept up in the course of other surveillance. But when it came to the president’s assertion that Mr. Obama authorized tapping of Trump Tower, he said, “clearly the president was wrong.”
His Senate counterpart, Senator Richard Burr of North Carolina, issued a joint statement on Thursday with Senator Mark R. Warner of Virginia, the top Democrat on the intelligence committee, saying they saw “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.”
In pointing the finger at Britain on Thursday, Mr. Spicer read from comments made by Mr. Napolitano on Fox this week. “Three intelligence sources have informed Fox News that President Obama went outside the chain of command,” Mr. Spicer read. “He didn’t use the N.S.A., he didn’t use the C.I.A., he didn’t use the F.B.I., and he didn’t use the Department of Justice. He used GCHQ.”
“What is that?” Mr. Spicer continued. “It’s the initials for the British intelligence spying agency. So simply, by having two people saying to them, ‘The president needs transcripts of conversations involved in candidate Trump’s conversations involving President-elect Trump,’ he was able to get it and there’s no American fingerprints on this.”
In London, outrage quickly followed. “It’s complete garbage. It’s rubbish,” Malcolm Rifkind, a former chairman of Parliament’s intelligence committee, told BBC News.
GCHQ was the first agency to warn the United States government, including the National Security Agency, that Russia was hacking Democratic Party emails during the presidential campaign. That warning stemmed from internet traffic out of Russia containing malware, British officials said.
British officials and analysts were surprised at the tough language in the GCHQ response, especially from an agency that traditionally refuses to comment on any intelligence matter.
There was some annoyance and eye rolling as well. Tim Farron, the leader of the Liberal Democrats, the junior partner in the last British coalition government, described Mr. Spicer’s repetition of the claims as “shameful” and said Mr. Trump was “compromising the vital U.K.-U.S. security relationship to try to cover his own embarrassment.”
Dominic Grieve, the current intelligence committee chairman in Parliament, noted that no president can instruct the GCHQ to act. He pointed to elaborate safeguards that prevent spying on the United States and require “a valid national security purpose” for any monitoring. “It is inconceivable that those legal requirements could be met in the circumstances described,” he said in a statement.
But Downing Street clearly wanted to avoid adding to any embarrassment in Washington while making it clear that Britain had no part in any such wiretapping, and that Britain would not be a party to circumventing the laws of a closely allied country. “We have a close relationship which allows us to raise concerns when they arise, as was true in this case,” the prime minister’s spokesman said. “This shows the administration doesn’t give the allegations any credence.”
British officials said that London had initiated calls of complaint and denial to the White House after Mr. Spicer’s briefing. They also said that British officials had discussed responding earlier, after Mr. Napolitano’s comments were made on air, but acted quickly after those remarks were repeated by the president’s official spokesman.
“I doubt if there will be any long-term damage — the intelligence links between the U.S. and the U.K. are just too strong,” said Peter Westmacott, a former British ambassador to the United States. “It was unfortunate that the White House spokesman repeated what he’s heard on Fox News without checking the facts. But once he’d done so, GCHQ had no choice but to set the record straight.”
An earlier version of this article misspelled the surname of Britain’s ambassador to the United States. It is Kim Darroch, not Derroch.