The office of former prime minister Tony Blair has rejected as "categorically absurd" allegations that he warned Donald Trump he was under surveillance by UK intelligence agencies.
The allegation is made in a new book – Fire and Fury: Inside the Trump White House – which includes explosive claims about feuds within the US President's inner circle.
Mr Trump himself fuelled the controversy after stating that his former senior adviser Steve Bannon – who told the book's author Michael Wolff that meetings between campaign officials and a lawyer linked to the Kremlin amounted to treason – had "lost his mind".
The Times newspaper reported that Mr Wolff's book contains an account of a meeting between Mr Blair and senior Trump aide Jared Kushner at the White House last February.
According to Mr Wolff, Mr Blair shared a "juicy rumour" that British intelligence agencies had spied on Trump campaign staff during the election, "monitoring its telephone calls and other communications and possibly even Trump himself".
The book also suggested that the former PM was after a role as Middle East adviser to the President at the time.
A month after the alleged meeting, then White House press spokesman Sean Spicer repeated claims made on Fox News that Barack Obama had asked British intelligence to spy on Trump Tower.
The Government's GCHQ surveillance centre dismissed those claims as "utterly ridiculous".
A spokesman for Mr Blair said the allegations in The Times "are a complete fabrication, have no basis in reality and are simply untrue".
In an excerpt from the book, Mr Bannon is quoted as saying a Trump Tower meeting between Donald Trump Jr and a group of lawyers was "unpatriotic" and "treasonous".
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White House spokeswoman Sarah Huckabee Sanders claimed the book was filled with "false and misleading accounts", and labelled Mr Bannon's accusation as "ridiculous".
Mr Bannon, viewed by many as the architect of Mr Trump's campaign, left the White House in August after a string of disagreements with the President and his allies.