Boris Johnson has said it is “absurd and shameful” that the statue of Sir Winston Churchill in Parliament Square was at risk of attack from anti-racism protesters.

Speaking after the memorial was boarded up to protect it ahead of more planned weekend demonstrations, the Prime Minister said on Twitter: “We cannot now try to edit or censor our past.”

In later comments, Mr Johnson warned people to stay away from future Black Lives Matter demonstrations, predicting they would “end in deliberate and calculated violence”.

A protective box was placed around the statue of the former premier, who led Britain during the Second World War struggle against the Nazis, after it was targeted during anti-racism protests last weekend.

It was vandalised with the words “Was a racist”, while the Cenotaph, which has also now been protected with hoarding, was also targeted.

The protests, sparked by the death of George Floyd in Minneapolis in the US, saw clashes between protesters and police in London, while in Bristol a statue of Edward Colston was pulled down and dumped in the harbour.

Mr Johnson said: “The statue of Winston Churchill in Parliament Square is a permanent reminder of his achievement in saving this country – and the whole of Europe – from a fascist and racist tyranny.

“It is absurd and shameful that this national monument should today be at risk of attack by violent protesters.

“Yes, he sometimes expressed opinions that were and are unacceptable to us today, but he was a hero, and he fully deserves his memorial.”

The Prime Minister voiced his opposition to the decision by a host of local authorities to remove a string of monuments and statues as the impact of the Black Lives Matter movement continues to be felt across the country.

The Conservative Party leader said to take statues down would “be to lie about our history”.

Guy’s and St Thomas’ hospitals in London announced they will remove two statues of their namesakes from public view due to their links to the slave trade.

Bournemouth, Christchurch and Poole Council has delayed plans to temporarily remove a statue of Scouts founder Robert Baden-Powell after angry residents vowed to fight to protect it.

The council had originally said it would move the statue from Poole Quay on Thursday over concerns it was on a target list compiled by anti-racism activists due to his associations with the Nazis and the Hitler Youth programme, as well as his actions in the military.

The sculpture features on a “topple the racists” website which lists more than 60 statues and memorials across the UK which they argue should be taken down, because they “celebrate slavery and racism”.

But Mr Johnson, in a series of social media posts, said: “We cannot pretend to have a different history.

“Those statues teach us about our past, with all its faults.

“To tear them down would be to lie about our history, and impoverish the education of generations to come.”

The PM, in an interview with broadcasters, also addressed the ongoing anti-racism demonstrations, arguing the protests had been “hijacked” by a “growing minority” and were being used “as a pretext to attack the police, to cause violence and to cause damage to public property”.

He added: “Whatever our feelings about the cause, we should not support a demonstration that is, in all probability looking at what has happened before, going to end in deliberate and calculated violence.”

More than 130 people have been arrested as over 155,000 people across the UK took part in almost 200 demonstrations, according to the National Police Chiefs’ Council (NPCC).

A total of 62 police officers have been injured in the protests triggered by the death of Mr Floyd.

The PM’s remarks come as reports in the Times suggested violent protesters could be jailed within 24 hours after Justice Secretary Robert Buckland and Home Secretary Priti Patel drew up plans based on the response to the 2011 London riots.

Metropolitan Police Commander Bas Javid, a Bristolian and brother of former chancellor Sajid Javid, promised a “robust” response to any disorder at protests over the coming days.

Mr Javid reminded would-be demonstrators that gatherings in groups larger than six were “unlawful” due to Covid-19 restrictions.

Meanwhile, Black Lives Matter campaigners have unveiled a billboard on Westminster Bridge Road in central London, near to Parliament, highlighting the plight of black people in the UK.

Forming the words “I can’t breathe” – uttered by Mr Floyd as he choked – the poster lists more than 3,000 names of people who have died in police custody, prisons, immigration detention centres and in racist attacks in the UK, as well as those who have died with coronavirus and the Grenfell Tower fire.

The display was put up after organisers cancelled an anti-racism protest in London’s Hyde Park on Saturday over fears it would be hijacked by far-right groups.

A similar protest is still expected to go ahead on Friday but London Mayor Sadiq Khan has pleaded with the public to stay at home.