MPs have urged the prime minister to apologise after he said the best way to honour Jo Cox, the MP murdered during the EU referendum campaign, was to get “Brexit done”.
He was also criticised for calling the law aimed at blocking a no-deal Brexit the “surrender bill”.
Labour MP Jess Phillips said the “bravest” thing for the prime minister to do would be to apologise.
Tory Party chairman James Cleverly said accusations had been “deeply unfair”.
Asking an urgent question in the Commons on the prime minister’s language, Ms Phillips said the “bravest and strongest thing to do” would be for the prime minister to apologise.
She said use of language which invoked “the war, such as betrayal and treachery” had “clearly been tested, and work-shopped and worked up and entirely designed to inflame hatred and division”.
She added she felt “pity” for those Conservative MPs who “have to toe his line”.
Another Labour MP Paula Sherriff, who challenged the prime minister to moderate his language on Wednesday, said she accepted “it is necessary for all us of to reflect” on the issue, admitting she has been known to make the “odd heckle”.
Responding to MPs, minister Kevin Foster said the government was working to ensure MPs “feel safe”, especially online.
A No 10 spokesman had earlier said: “The PM obviously made the broader point last night that he believes we need to get the issue of Brexit resolved because it was causing anxiety and ill-feeling in the country.”
He added that, whatever their views, politicians and those in public life “shouldn’t face threats or intimidation… it’s completely unacceptable”.
Speaker John Bercow said the culture in the Commons had been “toxic”.
He said passions were inflamed on both sides, the atmosphere had been “worse than any I’ve known” and urged MPs to “disagree agreeably”.
Earlier, Brendan Cox, the husband of murdered MP Jo Cox, said the Brexit debate had descended into a “bear pit of polarisation”.
MPs have rejected a motion to approve a three-day break for the Commons next week while the Conservatives stage their annual party conference by 306 votes to 289.
Mr Johnson was greeted by cheers when he addressed Conservative MPs at a meeting of the backbench 1922 Committee.
BBC political correspondent Chris Mason says Downing Street is not planning to shift away from using the term “surrender bill”.
Meanwhile, the longest-serving male and female MPs, Ken Clarke and Harriet Harman, have called for an inquiry, chaired by Mr Bercow, to discuss “protecting our democracy by guaranteeing the ability of MPs to go about their work without threat, harassment, violence or intimidation”.
Wednesday’s highly charged Commons debate came a day after the Supreme Court ruled Mr Johnson’s suspension of Parliament unlawful.
He was forced to cut short his visit to a UN summit in New York to return to the Commons following the decision.
The prime minister told MPs the court had been “wrong to pronounce on a political question at a time of great national controversy”.
He also challenged opposition parties to table a vote of no confidence or back a general election.
Speaking to Radio 4’s Today programme, Brendan Cox said “bad behaviour” was not limited to one side of the debate and said words such as “coup” and “fascism” are also “inflammatory”.
“This is something which has infected our politics and it’s this vicious cycle where language gets more extreme, responses get more extreme, it all gets hyped up,” he said.
“And the reason that it matters is because it has real world consequences.”
Conservative chairman Mr Cleverly said the debate over Brexit in the House of Commons had generated “a huge amount of temper on both sides of the Commons”.
“The best thing we can do to calm things down is to get it delivered, get it resolved,” he added.
He also said the accusations levelled at the prime minister were “deeply unfair” adding that he had never described people as “traitors”.
