Boris Johnson has declined to apologise for his language about Jo Cox and ducked a Commons debate on inflammatory rhetoric, instead attending a meeting of Tory MPs to say he will continue to use the phrase “surrender bill” to refer to the act passed to avoid a no-deal Brexit.

Johnson spoke at a meeting of the 1922 Committee of Conservative MPs the morning after being branded a disgrace for dismissing concerns about his inflammatory language in light of Cox’s murder by a far-right extremist.

In the Commons on Wednesday, he told one MP that her concerns about aggressive language fuelling violence were “humbug” and another that the best way to honour Cox was to “get Brexit done”.

Play Video 2:43 Outrage as Boris Johnson dismisses dangers of inflammatory language as 'humbug' - video

The prime minister addressed some of the criticism, saying there was a need to moderate violent language on all sides of the debate. But he was reported to have told Tory MPs on Thursday that he would continue to use his language about the Benn Act (formally called the European Union (Withdrawal) (No. 2) Act 2019) to stop a no-deal Brexit. He dubs it the “surrender bill” despite criticism that this paints his opponents in parliament as traitors guilty of a betrayal.

Johnson was met with shouts of “Will you apologise, prime minister?” from journalists as he left the meeting, but he walked away without commenting.

His senior adviser, Dominic Cummings, was shortly afterwards confronted on the parliamentary estate by the Labour MP Karl Turner, who said MPs including himself had received more death threats. Cummings responded: “Well, vote for a deal then.”

Johnson was even criticised by his own sister, Rachel, who told Sky: “I do think it was particularly tasteless for those grieving a mother, MP and friend to say the best way to honour her memory is to deliver the thing she and her family campaigned against.

Play Video 1:11 Boris Johnson's sister says his Jo Cox remarks were 'tasteless' – video

“I think it was a very tasteless way of referring to the memory of a murdered MP, murdered by someone who said ‘Britain first’, of the far-right tendency, which you could argue is being whipped up by this sort of language.

“My brother is using words like surrender and capitulation as if the people standing in the way of the blessed will of the people as defined by 17.4m votes in 2016 should be hung, drawn, quartered, tarred and feathered. I think that is highly reprehensible language to use.”

Tory MPs said the mood of Johnson’s meeting had been “largely supportive” but others sighed or raised their eyebrows when asked how he had performed.

Jo Cox's sister criticises Boris Johnson's Brexit rhetoric Read more

Paul Scully, the deputy chairman of the Conservative party, said the prime minister acknowledged there had been “a lot of words said, a lot of attacks on female MPs and on members of the families of female politicians”.

“But I think there’s also a sense of conflation of those in the opposition, wrapping that up with the robust debate and the acknowledgment that the surrender act is a surrender act because it is literally surrendering power to the EU.”

He added: “At the end of the day the surrender act is literally a backbench MP who has written a letter to give to the UK prime minister, which gives the EU permission to tell us when we can leave the EU. By any dictionary definition this surrenders power to the EU.”

As Johnson addressed his backbenchers, the Labour MP Jess Phillips brought an urgent question to the Commons on the subject of inflammatory language.

Rather than appearing himself, Johnson sent the junior minister Kevin Foster, who is responsible for the constitution.

Jeremy Corbyn said Johnson “has not respected this house by attending today”.

“The prime minister’s language and demeanour yesterday was nothing short of disgraceful,” the Labour leader said. “Three years ago our colleague Jo Cox was murdered by a far-right activist shouting: ‘Britain First. This is for Britain.’

“The language that politicians use matters – it has real consequences. To dismiss concerns from honourable members about the death threats they receive, and to dismiss concerns that the language used by the prime minister is being repeated in those death threats, is reprehensible.”

He accused Johnson of having “sought to entrench divisions” instead of calming them down.

“Not only should the prime minister comply with the law, he should come to this house and apologise for his conduct yesterday, which fell below the standards expected by the people of this country,” he said.

Phillips asked for Johnson and his advisers to meet her and Cox’s family so they could explain their grief and concerns about inflammatory language in politics.

“The use of language yesterday and over the past few weeks such as the surrender bill, such as invoking the war, such as betrayal and treachery, it has clearly been tested, and workshopped and worked up and entirely designed to inflame hatred and division,” she said. “I get it, it works, it is working. It is not sincere, it is totally planned, it is completely and utterly a strategy designed by somebody to harm and cause hatred in our country.

“When I hear of my friend Jo Cox’s murder and the way it has made me and my colleagues feel, and feel scared, described as humbug, I actually don’t feel anger towards the prime minister, I feel pity for those of you who have to toe his line.

“The people opposite me know how appalling it was to describe the murder of my friend as mere humbug.”

Play Video Jess Phillips: Boris Johnson's language is 'designed to inflame hatred' – video

Foster took a more conciliatory tone than Johnson, saying the murder of Cox was a “dreadful crime”, but he echoed the prime minister’s argument that delay over Brexit was causing tensions.

“The government is also considering what further steps are necessary to ensure the safety of parliamentarians and their staff,” he added. “Crucially this applies not only to the vicinities of parliament but also in constituencies and online.”

However, not all Tory MPs appeared to be intent on calming tensions. Sir Bernard Jenkin, a Eurosceptic backbencher, said MPs should not reference the murder of Cox to “try and make political points”.

MPs responded with shouts of outrageous when Jenkin said: “There is already a danger in these exchanges of it turning into a holier-than-thou competition.

“I think we should reflect on how much unhappiness and anxiety there is among members of the house, and that this is going to be expressed in various ways, and people are going to use robust and emotive language in order to express their views, and that is entirely understandable.

“Can I just make one request, that we no longer invoke the name of any person who has been the victim of attacks in order to try and make political points.”