* UK spy agency accused of "wire tapping" US President Trump
* PM May and GCHQ say accusation is "ridiculous"
* GCHQ makes rare public statement on the claims (Recasts with comments from May's spokesman)
By Elizabeth Piper and Michael Holden
LONDON, March 17 (Reuters) - British Prime Minister Theresa May has received assurances from the White House it would not repeat allegations that Britain's GCHQ spy agency had helped former U.S. President Barack Obama eavesdrop on Donald Trump, her spokesman said on Friday.
A spokesman for May said that the charge, made on Tuesday by Fox News analyst Andrew Napolitano, that the UK's signals intelligence agency GCHQ had helped Obama to wire tap Trump after his victory in last year's U.S. presidential election, was "ridiculous".
"We've made clear to the administration that these claims are ridiculous and they should be ignored and we've received assurances that these allegations will not be repeated," May's spokesman told reporters.
"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."
Representatives for the White House did not immediately reply to a request seeking comment following May's spokesman's remarks.
Trump, who became president in January, tweeted earlier this month that his Democratic predecessor had wiretapped him during the late stages of the 2016 campaign. The Republican president offered no evidence for the allegation, which an Obama spokesman said was "simply false".
On the "Fox & Friends" program, Napolitano, a political commentator and former New Jersey judge, said that rather than ordering U.S. agencies to spy on Trump, Obama had obtained transcripts of Trump's conversations from GCHQ so there were "no American fingerprints" on it.
White House spokesman Sean Spicer on Thursday quoted Napolitano's comments about GCHQ when he spoke to the media.
Britain's Daily Telegraph newspaper, citing unnamed intelligence sources, reported on its website that Spicer and Trump's national security adviser Lieutenant General Herbert McMaster had made formal apologies to Britain.
In a rare public statement, Britain's GCHQ, Britain's Government Communications Headquarters, the equivalent of the U.S. National Security Agency which monitors overseas electronic communications, said the claims should be ignored.
"Recent allegations made by media commentator Judge Andrew Napolitano about GCHQ being asked to conduct 'wire tapping' against the then President Elect are nonsense," said a spokesman for GCHQ, which never usually comments on criticism of its work beyond saying it always operates under a strict legal framework.
Reuters reported earlier this week that an unidentified British security official had denied the allegations about Trump. based in a futuristic building located in western England, is one of three main British spy agencies alongside the MI6 Secret Intelligence Service and the MI5 Security Service.
GCHQ has a close relationship with the NSA, as well as with the eavesdropping agencies of Australia, Canada and New Zealand in a consortium called "Five Eyes." (Editing by Guy Faulconbridge and Julia Glover)