Boris Johnson has been branded a disgrace for dismissing pleas from Labour MPs to stop using inflammatory language in light of the murder of Jo Cox, telling one that it was “humbug” and another that the best way to honour her was to “get Brexit done”.

Johnson caused uproar in the House of Commons after he responded dismissively to Labour MP Paula Sherriff, who made a heartfelt speech calling on him to stop using language such as “surrender”, “traitor” and “betrayal” in relation to Brexit.

He also drew gasps when telling Labour’s Tracy Brabin, who was elected to Cox’s seat following the MP’s murder by a far-right extremist a week before the EU referendum, that “the best way to honour the memory of Jo Cox and to bring this country together is, I think, to get Brexit done”.

Before her death, Cox had campaigned to remain in the EU. Her widower, Brendan Cox, swiftly condemned the prime minister’s remarks, saying it had left him feeling sick.

Brendan Cox (@MrBrendanCox) Feel a bit sick at Jo’s name being used in this way. The best way to honour Jo is for all of us (no matter our views) to stand up for what we believe in, passionately and with determination. But never to demonise the other side and always hold onto what we have in common.

Johnson’s attitude was lambasted by Jo Swinson, the Lib Dem leader, who called him a “disgrace” and Nicola Sturgeon, the SNP first minister, who said she felt “disgust watching Johnson”, describing him as “untrustworthy, craven, not a shred of concern for the consequences of his words or actions”. Dawn Butler, the shadow secretary for women and equalities, said his reaction showed that Johnson was “a cruel, uncaring, spoilt man”.

Swinson revealed on Wednesday that she had reported to police a death threat against her young child.

Amber Rudd, who resigned from Johnson’s cabinet earlier this month, told ITV the prime minister was being “dishonest and dangerous” in his use of language.

Jess Phillips, the Labour MP and women’s rights campaigner, highlighted an anonymous death threat she had personally received, quoting Johnson’s image that he would rather be dead in a ditch than fail to deliver Brexit. “That is what will happen to those who fail to deliver Brexit,” it said.

“10 Downing Street might think we are ‘humbugs’ about his words but they are literally being used in death threats against me,” she said.

“I get death threats and still I stand up. I don’t surrender to fear and aggression. I don’t surrender to lowest common denominator of fear to votes. I don’t surrender to bullies who call me names. It is not I who have surrendered, it is Boris Johnson. He has surrendered his dignity.”

John Bercow, the Speaker, implicitly rebuked Johnson and told MPs that he had also received threats: “Each and every one of us has a responsibility to weigh his or her words ... with care, eloquence, humour but in terms that demonstrate respect for those who hold a point of view that differs from our own.”

Jeremy Corbyn called on the Speaker to call together the leaders of all parties to issue a joint declaration “opposing any form of abusive language or threats and to put this message out to our entire community that we have to treat each other with respect”.

“If we don’t, then what happens is those on our streets who would do violence feel emboldened to do it and the most vulnerable people in our society suffer as a result of it,” the Labour leader added.

Bercow said he was “very open” to the idea of convening a meeting to draw up a house-wide public statement.

After an aggressive debate in parliament, with the prime minister accusing the opposition of signing a “surrender act” over Brexit, Sherriff received applause from the opposition benches for calling on Johnson to stop using such language.

“We should not resort to using offensive, dangerous or inflammatory language for legislation that we do not like and we stand here under the shield of our departed friend with many of us in this place subject to death threats and abuse every single day,” she said.

“And let me tell the prime minister that they often quote his words ‘surrender act’, ‘betrayal’, ‘traitor’ and I for one am sick of it. We must moderate our language and it has to come from the prime minister first. He should be absolutely ashamed of himself.”

Johnson replied with a half-smile, saying: “I have to say Mr Speaker I’ve never heard such humbug in all my life.”

He was also confronted by Brabin, who criticised him for using language such as “surrender”, arguing it cast his opponents as traitors.

No apologies. Labour fury as Boris Johnson goes on the attack Read more

“As the woman who has taken over a seat left by our dear friend Jo Cox, can I ask him in all honesty as a human being please, please will he going forward moderate his language so that we will all feel secure when we’re going about our jobs?” she said.

However, Johnson responded by repeating some of the language and suggesting the answer was to deliver Brexit.

“Of course there will be an attempt to try to obfuscate the effect of this Act, but it does – the capitulation act, or the surrender act or whatever you want to call it – it does, I’m sorry, but it greatly enfeebles, it greatly enfeebles this government’s ability to negotiate.

“But what I will say is that the best way to honour the memory of Jo Cox and indeed the best way to bring this country together would be, I think, to get Brexit done.”

Commons leader, Jacob Rees-Mogg, condemned the abuse that MPs had received as “deeply, deeply unpleasant and troubling”.

He said: “We all have a responsibility to be mild in our language when we’re speaking in this house or outside.

“I’m afraid to say it’s something where all sides err from time to time and it would be invidious to pick on individual examples but we have a responsibility of leadership.”

Former Tory Anna Soubry raised a point of order to criticise the prime minister’s language: “It takes a lot to reduce this honourable member to tears ... but I am not alone tonight. There are others who have left the estate such has been the distress.”