U.S. President Donald Trump has stuck by his claim that the Obama administration wiretapped his phones in Trump Tower with the help of British security, despite a complaint by British authorities that such an assertion is "ridiculous."

Trump spoke to reporters Friday at a news conference with German Chancellor Angela Merkel. Questioned by a reporter about the allegation, which Trump first made in a tweet on March 4, Trump answered by referencing a wiretapping scandal in which U.S. security officials were found to be listening in on Merkel's private conversations.

"As far as wiretapping, I guess, by this past administration, at least we have something in common, perhaps," Trump said to Merkel.

Merkel did not answer and a few reporters in the room laughed nervously.

Germany's Chancellor Angela Merkel, left, gives U. Germany's Chancellor Angela Merkel, left, gives U.S. President Donald Trump a look after he suggested they might have something in common, as he answered a question about his accusation that he had been wiretapped by former President Barack Obama, during their joint news conference in the East Room of the White House in Washington, March 17, 2017. Germany's Chancellor Angela Merkel, left, gives U.S. President Donald Trump a look after he suggested they might have something in common, as he answered a question about his accusation that he had been wiretapped by former President Barack Obama, during their joint news conference in the East Room of the White House in Washington, March 17, 2017.

On Thursday, White House spokesman Sean Spicer cited a Fox News report to back up claims that the British spy agency, known as GCHQ, was involved in wiretapping Trump Tower.

Fox host Andrew Napolitano claimed that "three intelligence sources have informed Fox News that President [Barack] Obama went outside the chain of command" to order the surveillance and that GCHQ was involved.

A spokesman for GCHQ denied the claims, saying, "Recent allegations made by media commentator Judge Andrew Napolitano about GCHQ being asked to conduct 'wiretapping' against the then-president-elect are nonsense."

A spokesman for British Prime Minister Theresa May on Friday called Trump's claims "ridiculous" and said it would be impossible for Britain to spy on a U.S. citizen because of an agreement signed between the two countries. The spokesman said Britain had received assurances from the White House that the claims would not be repeated.

Satellite dishes are seen at GCHQ's outpost at Bud FILE - Satellite dishes are seen at GCHQ's outpost at Bude, close to where trans-Atlantic fiber-optic cables come ashore in Cornwall, southwest England, June 23, 2013. FILE - Satellite dishes are seen at GCHQ's outpost at Bude, close to where trans-Atlantic fiber-optic cables come ashore in Cornwall, southwest England, June 23, 2013.

The White House has produced no evidence of its claim, insisting that it is only repeating "public reports."

Friday afternoon, a Fox News anchor read a statement on the air saying, "Fox News knows of no evidence of any kind that the now president of the United States was surveilled at any time, in any way, full stop."

Also Friday, the Justice Department said it has complied with requests from congressional Intelligence and Judiciary committees to provide information on any surveillance from the 2016 election.

The two top senators on the Senate Intelligence Committee, Republican Richard Burr and Democrat Mark Warner, said Thursday: "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."

Their statement followed one from House of Representatives Speaker Paul Ryan, who also dismissed the president's explosive claim that Obama ordered the eavesdropping. "We've cleared that up, that we see no evidence of that," Ryan said.

Obama has dismissed the allegation as "simply false."