Downing Street has declined to apologise for Prime Minister Boris Johnson's words in the House of Commons last night.
Mr Johnson provoked gasps in the Commons and was widely condemned after claiming the best way to honour murdered MP Jo Cox would be to "get Brexit done".
The prime minister's remark came after several MPs drew upon the memory of Ms Cox when urging him to curb his "violent" and "dangerous" language.
Brendan Cox, widower of Ms Cox, said he felt "a bit sick at Jo's name being used in this way" while the Commons heard MPs were reduced to tears and some left the parliamentary estate due to the "distress" caused.
Liberal Democrat leader Jo Swinson described the PM's words as "sickening" and appeared to fight back tears as she revealed she has reported to police a threat against her child.
Labour's Paula Sherriff initially criticised Mr Johnson for his repeated use of "surrender act" when describing legislation designed to prevent ministers forcing through a no-deal Brexit on 31 October.
She warned against using such language and mentioned Ms Cox before highlighting that many MPs are subject to death threats and abuse.
But Mr Johnson labelled her remarks "humbug", which prompted an angry response in the chamber - with shouts of "shame" emerging.
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Labour's Tracy Brabin, who was elected to the seat after Ms Cox was killed by a man with far-right sympathies during the 2016 EU referendum campaign, also called for the PM to moderate his language.
She said: "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."
Mr Johnson replied: "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 to bring this country together would be, I think, to get Brexit done."
Earlier, Ms Sherriff said the PM had "continually used pejorative language to describe an Act of Parliament passed by this House".
She added: "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.
"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."
She added: "He should be absolutely ashamed of himself." Her words prompted applause from the opposition benches.
Mr Johnson said: "I have to say, Mr Speaker, I've never heard such humbug in all my life."
The PM was later urged to clarify his remarks on Ms Cox, to which he said: "I can, I think, to explain exactly what I mean because I believe that the continuing failure to deliver on the mandate of the people greatly exacerbated feelings and the best way to reduce that tension is, as I say, to get it done and then the whole country can move on."
Anna Soubry, leader of the Independent Group for Change, raised a point of order to say: "It takes a lot to reduce this honourable member to tears and it gives me no pleasure saying that."
She added: "I am not alone tonight, there are others, I believe, who has left the estate, such has been the distress."
Labour leader Jeremy Corbyn called on the Speaker to "call together the leaders of all parties in this House 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".
Mr Bercow said he was "very open to convening a meeting of senior colleagues for the purpose of a House-wide public statement".
Paying his own tribute, Mr Bercow said: "I don't think any of us in this chamber will entirely forget or overcome our horror, revulsion and distress at what happened to a wonderful human being and the most dedicated of public servants.
"She was murdered for what she believed, the values she held and for her effectiveness in campaigning for them.
"We do not in any circumstances ever want to witness a repeat of that."
Meanwhile, Mr Johnson has defended his decision to use the term "surrender act" when speaking about a new law that forces him to seek a Brexit delay if he fails to secure a deal to leave the European Union.
At a meeting of the 1922 Committee of Conservative politicians yesterday, Mr Johnson won support for his argument that the law undermined his negotiating position in Brussels and that he was within his rights to describe is as a "surrender act".
Mr Johnson was criticised by opposition politicians and some in his own Conservative Party for using such language yesterday, with some saying it not only deepened divisions but also could incite violence against those working in parliament.
Mr Johnson hails what he describes as progress in the Brexit talks, but EU officials say Britain has yet to come up with "legal and operational" proposals to solve the thorniest issue of customs arrangements for the new border between Northern Ireland and the Republic Ireland after Brexit.
Today, the prime minister's official spokesman 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."
Asked if the prime minister's comments risked fuelling a bad reaction, the spokesman said: "The PM is very clear that whatever their views no MPs or anyone else in public life should face threats or intimidation. It's completely unacceptable."
Meanwhile, Boris Johnson's sister Rachel Johnson hit out at her brother's behaviour, claiming that he was employing "strongman" tactics and using the Commons despatch box as a "bully pulpit".
"It's not the brother I see at home. It's a different person," she told BBC Radio 4's World at One.
"What we saw yesterday and today in the Commons is a very divided country.
"But to say that Parliament is at fault is not helpful, because Parliament is also divided and it's reflecting the division in the country."
She added: "I think that what we are seeing is an executive that is so keen to deliver Brexit in any shape or form, to get the country out of the EU, to deliver up on that promised land, that they will do anything to justify that end."
