Donald Trump’s senior advisers should be tried for treason if it is proved they colluded with Russia to influence the outcome of the US presidential election, Hillary Clinton’s former campaign manager has said.

Robby Mook, who managed the Democrat’s campaign from April 2015 until the November 2016 election, said any proof Mr Trump’s team were aware of alleged Russia plans to try to influence the election must result in charges of treason – a crime that can carry the death penalty.

“We need to find out exactly what happened," Mr Mook told The Hill. "If US campaign aides helped the Russians, knew about the Russians plans, or asked the Russians to intervene in any way, they should be prosecuted for treason and measures should be put in place to make sure this never happens again.”

"If we allow this practice to continue, Russia and other foreign nations could have a dangerously powerful influence on our legislative and executive branches.

"We complain all the time about the influence of super pacs and campaign donations in our politics, which are real, because they punish officials who act contrary to their interests. Now, foreign powers are attempting to gain a similar influence and they must be stopped."

Vladimir Putin, the Russian President, had interfered in the election to punish Hillary Clinton, “who he regarded as an enemy of his regime”, Mr Mook alleged.

"He was punishing her for actions she took on behalf of the American people as our Secretary of State," he added.

Moscow has consistently denied having any involvement in the US presidential election.

In pictures: Protests, pomp and Donald Trump Show all 30 1 /30 In pictures: Protests, pomp and Donald Trump In pictures: Protests, pomp and Donald Trump President-elect Donald Trump acknowledges guests as he arrives on the platform at the US Capitol in Washington DC Getty Images In pictures: Protests, pomp and Donald Trump Donald Trump is sworn in as the 45th president of the United States by Chief Justice John Roberts as Melania Trump looks on during the 58th Presidential Inauguration at the U.S. Capitol in Washington AP In pictures: Protests, pomp and Donald Trump President Donald Trump shakes hands with Justice John Roberts after taking the oath at inauguration ceremonies swearing in Trump as the 45th president of the United States Reuters In pictures: Protests, pomp and Donald Trump President Donald Trump raises his fists after his inauguration on the West Front of the U.S. Capitol Getty In pictures: Protests, pomp and Donald Trump U.S. President-elect Donald Trump greets outgoing President Barack Obama before Trump is inaugurated during ceremonies on the Capitol in Washington Reuters In pictures: Protests, pomp and Donald Trump resident-elect Donald Trump arrives on the platform of the US Capitol in Washington DC Getty Images In pictures: Protests, pomp and Donald Trump Attendees partake in the inauguration ceremonies to swear in Donald Trump as the 45th president of the United States at the U.S. Capitol in Washington DC Reuters In pictures: Protests, pomp and Donald Trump US President Donald Trump delivers his inaugural address during ceremonies at the US Capitol in Washington DC Getty In pictures: Protests, pomp and Donald Trump U.S. President Donald Trump waves with wife Melania during the Inaugural Parade in Washington DC Reuters In pictures: Protests, pomp and Donald Trump Protesters registered their rage against the new president Friday in a chaotic confrontation with police who used pepper spray and stun grenades in a melee just blocks from Donald Trump's inaugural parade route. 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Earlier this week James Comey, the Director of the Federal Bureau of Investigation (FBI), admitted his organisation was investigating possible collusion between Mr Trump’s team and Moscow in the lead-up to the election.

Former Clinton campaign officials reacted angrily to Mr Comey's admission that he had sought Department of Justice approval to publicly confirm the investigation into Mr Trump and Russia - something he did not do before announcing, just days before presidential election, new enquiries into Ms Clinton's use of a private email server.

Mr Trump and his team have been dogged by allegations that Russia interfered on their behalf.

Michael Flynn, the President’s choice for national security adviser, was also forced to resign in February after he was revealed to have lied about the nature of his conversations with Sergey Kisylak, the Russian ambassador to the US.

Jeff Sessions, the US Attorney General, also faced calls to step down after he was also found to have met with Mr Kislyak during the campaign.

US media reports claim intelligence intercepts show other, as yet unnamed, Trump aides also had contact with Moscow officials.

Mr Trump and his team have denied any suggestion they had contact with the Russian state relating to the election campaign.