Donald Trump is unlikely to finish his first term as President, according to a leading Democrat.

Senator Mark Warner, the vice chairman of the Senate Intelligence Committee, privately told friends he puts the odds at two to one against the President completing a full term, the New Yorker reported.

Mr Warner's spokesperson did not deny he had made the remarks, but told the paper the Senator was "not referring specifically to the Russia investigation, but rather the totality of challenges the President is currently facing."

The Senator previously said the Kremlin had paid an army of more than 1,000 people to create fake anti-Hillary Clinton news stories targeting key swing states.

Former Labor Secretary Robert Reich said there was a "growing possibility Trump could be impeached" as he shared the New Yorker article on Twitter.

It comes after a source told The Guardian the investigation now has "specific, concrete and corroborative evidence of collusion."

The evidence allegedly proves discussions took place "between people in the Trump campaign and agents of [Russian] influence relating to the use of hacked material," the source told the paper.

It also emerged the British Government was passed a dossier detailing alleged collusion between the Kremlin and Donald Trump in December.

The document alleges the existence of a Russian programme of "cultivating, supporting and assisting" Mr Trump as he campaigned for the presidency.

Mr Trump has dismissed the allegations as "fake news."