Former foreign minister Alexander Downer acted without clearance from Australian officials when he contacted United States diplomats four years ago to raise concerns about potential Russian interference in the US presidential election.

A new memoir by former prime minister Malcolm Turnbull reveals that Mr Downer raised his concerns directly with the US embassy in London in July 2016 but had "no authority from Canberra" to do so.

Former Australian foreign minister Alexander Downer. Credit:AP

The move was crucial to the launch of an FBI investigation into the Russian support for the election of US President Donald Trump, who dismissed the inquiry as a "witch-hunt" and ordered an inquiry into the affair.

Mr Downer, the Australian High Commissioner to the United Kingdom at the time, met Trump aide George Papadopoulos in London in May 2016 and was told the Russians had "damaging" material on Democrat candidate Hillary Clinton.