FBI probe into alleged Russian meddling in US elections sparked by tip-off after 'heavy-drinking session' in London bar

The FBI investigation into alleged Russian meddling in the US presidential election began after a tip-off from an Australian diplomat following a night of "heavy drinking" at a London bar with Donald Trump's campaign adviser, according to the New York Times.

Trump campaign adviser George Papadopoulos reportedly told Alexander Downer, Australia's top diplomat in Britain, that Russia had "dirt" on Democratic candidate Hillary Clinton in the form of thousands of emails during a meeting in May 2016.

Australia later informed the FBI after the Democratic emails were leaked. The Times report cited four current and former US and foreign officials with direct knowledge of the Australians' role.

"The hacking and the revelation that a member of the Trump campaign may have had inside information about it were driving factors that led the FBI to open an investigation in July 2016," the Times said.

White House lawyer Ty Cobb declined to comment, saying in a statement that the administration is continuing to co-operate with the investigation.

Papadopoulos has pleaded guilty to lying to the FBI and is a co-operating witness. President Trump called Papadopoulos a "low level volunteer" who was "proven to be a liar".

Court documents unsealed two months ago show he met in April 2016 with Joseph Mifsud, a professor in London who told him about Russia's cache of emails.

The Times said Papadopoulos shared this information with Mr Downer, but it was unclear whether he also shared it with anyone in the Trump campaign.