US President Donald Trump denies that his campaign colluded with Russia.

A tip from former Australian opposition leader Alexander Downer appears to have helped persuade the FBI to investigate Russian meddling in the United States election, according to the The New York Times.

The newspaper says Trump campaign adviser George Papadopoulos told Downer, who led the Liberal Party for eight months in 1994 and 1995 and is now Australia's High Commissioner to the UK, that Russia had thousands of emails incriminating Hillary Clinton.

Australia passed that on to the FBI. The Times says the revelation that a Trump campaign member may have had inside information about the hacking of Democratic emails helped to spark the Russia probe.

AFR Trump campaign adviser George Papadopoulos reportedly told Alexander Downer, who led the Liberal Party for eight months in 1994 and 1995 and is now Australia's High Commissioner to the UK, that Russia had thousands of emails incriminating Hillary Clinton.

Papadopoulos has pleaded guilty to lying to the FBI and is a co-operating witness in the investigation.

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

The Times says Papadopoulos shared this information with Downer.

Earlier this month it was announced that Australia's attorney-general, George Brandis, will take over Downer's post in the UK.