BORIS Johnson has “unreservedly condemned” Donald Trump’s incitement of the rioting in Washington as Joe Biden insisted the violent mob who stormed the Capitol were not protesters but “domestic terrorists”.

The Prime Minister, criticised by Labour for being “spineless” in his initial reaction to the violence on Capitol Hill, which resulted in the deaths of four people, spoke out directly against Mr Trump at a Downing St press conference.

He said: “Insofar as he encouraged people to storm the Capitol and insofar as the President consistently has cast doubt on the outcome of a free and fair election I believe that was completely wrong.

“I unreservedly condemn encouraging people to behave in the disgraceful way that they did in the Capitol. And all I can say is I’m very pleased that the President-elect has now been duly confirmed in office and that democracy has prevailed.”

Earlier, Nicola Sturgeon, who described the scenes in the US capital as “utterly horrifying,” said: “What we witnessed weren't just scenes of horrible breachs of law and order, we actually witnessed the President of the United States inciting insurrection in his own country and for many people it will take some time to get our heads round that."

The First Minister described Mr Trump’s time in office as a “dark period in American history,” and added: “Thankfully, there’s only a matter of days of his presidency left.”

In America, reports suggested members of the President’s own Cabinet were considering whether to forcibly remove him from office using the 25th Amendment.

Such an unprecedented move would require the support of a majority of the ministers, including Mr Pence, who as Vice President would take over as President.

Given there are only 12 days to go to Mr Biden’s inauguration, the suggestion might come to nothing with fears it could spark a backlash from Trump supporters. However, several Democrats are backing the move. Some 17 Democrat congressmen have already signed a letter urging Mr Pence to invoke the 25th.

Ted Lieu, a Democrat Congressman from California, called on the Vice-President to begin the proceedings to oust Mr Trump from office, saying: “You need to start the 25th Amendment. Donald Trump is detached from reality.”

Meanwhile, Joe Biden, speaking from his home state of Delaware, described the events of Wednesday as "one of the darkest days in the history of our nation" and "an assault, literally, on the citadel of liberty".

The President-elect said: "It was not dissent, it was not disorder, it was chaos," saying those at the Capitol were not protesters but a "riotous mob" and "domestic terrorists".

Reflecting concerns at how easily the rioters stormed the Capitol, Mr Biden noted how the mainly white mob were not treated aggressively by police partly due to their race.

"Nobody could tell me that if it was a group of Black Lives Matter protesters, they wouldn't have been treated very differently than the thugs that stormed the Capitol yesterday."

On Thursday, a seven-foot tall security fence was being erected outside Congress, something lawmakers have long resisted, but now has been deemed necessary after police failed to prevent the storming of the building.

Leading Democrat Nancy Pelosi, Speaker of the House of Representatives, piled pressure on the President’s ministers to resign. "Do they stand by these actions? Are they ready to say for the next 13 days that this dangerous man can do more harm to our democracy?" she asked.

Transport Secretary Elaine Chao was the first to resign, saying America had “experienced a traumatic and entirely avoidable event as supporters of the President stormed the Capitol building following a rally he addressed…It has deeply troubled me in a way that I simply cannot set aside."

Responding to the attack on Capitol Hill, a spate of officials also resigned their roles in disgust.

One, Mick Mulvaney, the US special envoy to Northern Ireland, made clear that he simply could not remain in his post following the “insurrection”.

He said: “Donald Trump did not build a bomb that went off yesterday, he did not build the fuse, but he did light it.”

Facebook announced it was blocking the President “indefinitely and for at least the next two weeks” from its social network.

Mark Zuckerberg, the company’s boss, explained: “We believe the risks of allowing the President to continue to use our service during this period are simply too great.”

Mr Trump was also temporarily banned from Twitter yet despite this he managed to relay a tweet via Dan Scavino, a White House adviser, which read: “Even though I totally disagree with the outcome of the election, and the facts bear me out, nevertheless, there will be an orderly transition on January 20th.

“I have always said we would continue our fight to ensure that only legal votes were counted. While this represents the end of the greatest first term in presidential history, it’s only the beginning of our fight to Make America Great Again!”

The message was notable for containing no condemnation of the rioters’ violence in Washington.

Wednesday’s rampage interrupted proceedings on Capitol Hill for six hours but in the early hours of this morning after Congress resumed, its members formally certified Mr Biden as the new President and Kamala Harris as the Vice-President.

Thirteen Republican senators and dozens of party representatives had planned to force a debate and votes on the ballots in up to six states.

However, the assault on the Capitol made some Republicans reconsider an attempt to overturn Mr Biden's win and challenges were only lodged against the results in Arizona and Pennsylvania. Both efforts lost overwhelmingly.

The formal certification followed the election of two Democrat senators in the Georgia run-offs, Raphael Warnock and John Ossoff. Their victories mean the Democrats will control both the House of Representatives and the Senate for the first two years of the Biden presidency, giving it a major boost to get laws through both Houses.

The violence in Washington began shortly after Mr Trump repeated his unfounded claims of election fraud to thousands of rallying demonstrators he had invited to the US capital. Many then surged to the Congress building after he incited them to go there as lawmakers were debating the electoral votes.

The scenes in Washington shocked America, Republicans as well as Democrats.

Phil Scott, the Republican Governor of Vermont, said: “The fabric of our democracy and the principles of our republic are under attack by the President. Enough is enough. President Trump should resign or be removed from office by his Cabinet or by the Congress.”

William Barr, the former Attorney General and one of Mr Trump’s most ardent supporters, also condemned his conduct, saying it was a "betrayal of his office and supporters". He added: “Orchestrating a mob to pressure Congress is inexcusable."