LONDON — Prime Minister Boris Johnson of Britain on Friday stirred a fraught debate over symbols of his country’s past, accusing protesters of seeking to “censor our past” and telling them it was “absurd and shameful” that a statue of Winston Churchill needed to be covered to protect it from being vandalized.
In series of eight Twitter posts, Mr. Johnson lavished praise on the wartime leader and responded to those who recently tore down the statue of a 17th-century slave trader in Bristol by insisting that the country’s imperial history should not be censored or edited.
Mr. Johnson has been on the defensive since the killing by the police of George Floyd in Minneapolis, an act that prompted demonstrations in Britain, including one in London in which protesters daubed the words “was a racist” after Churchill’s name on a statue near Parliament.
Regarded by many as Britain’s greatest leader because of his stewardship of the country during World War II, Churchill was also a fervent imperialist and many historians acknowledge that he expressed racist views.
“Churchill clearly made racist statements,” said Steven Fielding, a professor of political history at the University of Nottingham, while adding that the wartime leader is such a popular and prominent figure in Britain that Mr. Johnson stands to gain politically from defending him.
Though Churchill sometimes expressed opinions that would be “unacceptable to us today,” Mr. Johnson wrote, his statue “is a permanent reminder of his achievement in saving this country — and the whole of Europe — from a fascist and racist tyranny.”
But Mr. Johnson has used racist language himself in the past, making him at best a tainted arbiter on race issues. As a columnist in 2002, he once referred to “cheering crowds of flag-waving piccaninnies,” an offensive term for a black child, and to African people as having “watermelon smiles.”
On Friday, Nick Thomas-Symonds, who speaks for the opposition Labour Party on home affairs issues, called on Mr. Johnson to show national leadership, adding that “this means recognizing the deep hurt so many black people in our country have spoken so powerfully about.”
Mr. Johnson weighed in as more protests were expected and at a time when some Britons are questioning everything from their imperial past to xenophobic statements in TV shows of earlier eras.
Ahead of anticipated demonstrations, and counterprotests from right wing groups, London’s mayor, Sadiq Khan, ordered the precautionary covering of several statues, including those of Churchill and Nelson Mandela, and of monuments, including the Cenotaph, a war memorial near Downing Street.
In a statement, Mr. Khan said he was extremely concerned that protests in central London not only risk spreading the coronavirus, but could lead to disorder, vandalism and violence. “Extreme far-right groups who advocate hatred and division are planning counterprotests, which means that the risk of disorder is high,” he said.
Mr. Johnson also has urged people to stay away, claiming that the largely peaceful protests have been “hijacked by extremists intent on violence.” He also tweeted that “Whatever progress this country has made in fighting racism — and it has been huge — we all recognize that there is much more work to do.”
Compared with President Trump, Mr. Johnson uses Twitter sparingly, normally to communicate government policy rather than personal views.
But he seemed to make an exception on Friday to defend the legacy of his political idol, Churchill, who was the subject of one of Mr. Johnson’s books.
“We cannot try to edit or censor our past,” he added, “We cannot pretend to have a different history. The statues in our cities and towns were put up by previous generations. They had different perspectives, different understandings of right and wrong. But those statues teach us about our past, with all its faults,” he said.
The comments are likely to prove popular within Mr. Johnson’s Conservative Party, where there is growing discontent over the government’s handling of the Covid-19 pandemic and its catastrophic economic fallout.
Britain is struggling to emerge from lockdown. New figures on Friday showed that the British economy shrank by one-fifth in April, the largest monthly contraction on record.
Conservatives, however, are more united in their reaction to the protests and the culture wars that broke out following Mr. Floyd’s killing.
After protesters wrote that Churchill was a racist on the statue in London, several Tory lawmakers who represent northern working-class areas headed to Parliament Square armed with sponges and water to clean the monument.
Mr. Floyd’s killing has also prompted a broader soul-searching about the extent to which elements of British history and culture exclude and alienate minority groups.
In a move that has provoked criticism, UKTV decided to remove one episode of a 1970s comedy show, “Fawlty Towers,” from its streaming platform while it conducts a review of language and racial slurs. Critics say that the show aimed to satirize racism but other broadcasters, too, have been sifting through and removing content deemed offensive.
“We are in a febrile situation, a unique situation in terms of Covid-19, in terms of the economy and in terms of leaving the European Union,” said Mr. Fielding, referring to Britain’s departure from the bloc in January. “Everything is up for grabs: national identity, the economy, and who we are.”