US Attorney General Pam Bondi has ordered prosecutors to open legal proceedings into allegations that political opponents of Donald Trump may have conspired to falsely accuse him of colluding with Russia in the run-up to the 2016 presidential election.

According to the BBC's US partner CBS News, prosecutors will submit evidence to a grand jury, a group of members of the public who will decide whether formal charges will be filed.

It is unclear, however, what those charges might be and who could be charged.

Trump was elected president in the 2016 election, beating Democratic candidate Hillary Clinton. He has always accused political foes of smear over the so-called Russia Gate allegations.

Last month, US Director of National Intelligence Tulsi Gabbard accused former President Barack Obama and his national security team of a "years-long coup" against Trump.

Gabbard alleged that intelligence about Russian meddling in the 2016 White House election had been politicised by the Obama White House to falsely tie Trump to Russia.

Trump reacted by accusing Obama of "treason" - and an Obama spokesman called that claim "bizarre".

Democrats said nothing in Gabbard's findings invalidated a US intelligence assessment in January 2017 concluding that Russia had sought to damage Clinton's campaign and boost Trump in the vote three months earlier.

A 2020 bipartisan report by the Senate intelligence committee also found that Russia had tried to help Trump's 2016 campaign.

Fox News reported last month that ex-CIA Director John Brennan and ex-FBI Director James Comey were under criminal investigation relating to the Trump–Russia probe. Both have long denied any wrongdoing and accuse Trump of subverting the justice system.

Half of Trump's first presidency was overshadowed by an investigation from his own justice department into whether he had conspired with Russia to sway the 2016 outcome.

The resulting Mueller report found no proof that Trump or his campaign had co-ordinated with the Kremlin, and no-one was charged with such crimes.

The debate over Russiagate was reinvigorated last week when an appendix to another justice department investigation into the affair was declassified.

The 29 pages from Special Counsel John Durham's inquiry cites a March 2016 memo from a US intelligence source stating that Hillary Clinton had approved a plan to smear Trump as a Russian asset.

Durham cites "what appear or purport to be original" emails that hackers affiliated with Russian intelligence might have obtained from an employee with a non-profit organisation run by liberal donor George Soros.

One of the messages appeared to have been sent by Leonard Benardo, senior vice-president at Open Society Foundations, Soros' philanthropic arm. It apparently refers to a Clinton foreign policy adviser, Julianna Smith.

The email, dated 26 July 2016, reads: "Julie says it will be a long-term affair to demonize Putin and Trump. Now it is good for a post-convention bounce. Later the FBI will put more oil into the fire."