The unusual move by the agency came after White House Press Secretary Sean Spicer cited claims first made on US TV channel Fox News earlier this week.
GCHQ responded by saying the allegations were “nonsense, utterly ridiculous and should be ignored”.
Donald Trump has claimed that Trump Tower in New York was under surveillance.
‘Chain of command’
The GCHQ claims were initially made by former judge Andrew Napolitano.
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.”
A GCHQ spokesman said: “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.”
Source: BBC
