The prime minister's remark in relation to murdered MP Jo Cox has left a former Conservative Welsh secretary "shocked".
MP Stephen Crabb said Boris Johnson had "a duty to reduce the level of poison in our politics".
The prime minister angered many MPs by using words such as "surrender" and "betray" as he addressed the Commons.
A Labour MP referred to her colleague's murder as she criticised Mr Johnson's remarks but he dismissed her intervention as "humbug".
The prime minister said the best way to honour the memory of Jo Cox - who campaigned for Remain - and bring the country together, was "to get Brexit done".
Conservative MP for Monmouth David Davies defended Mr Johnson, saying he thought Labour was wrong to raise Jo Cox's name in connection with the debate.
Preseli Pembrokeshire MP and former Welsh Secretary Mr Crabb told BBC Wales: "Boris has strong support among Conservative MPs for trying to unblock Brexit.
"But he also has a duty as prime minister to try to bring unity to our country and reduce the level of poison in our politics.
"I was shocked by the way he responded to the remarks about Jo Cox."
In a BBC Wales interview later, he added: "I do think he probably does need to apologise or at least clarify the context that he made [the comments] in.
"There are a lot of female MPs who every single day live with threats and incredibly dangerous nasty emails being sent to them and the prime minister has got a duty as the prime minister of the whole of the United Kingdom to defend all parliamentarians and set the right tone in this very difficult matter."
During Wednesday's debate, Labour's Paula Sheriff pointed to a plaque in the chamber commemorating Labour MP Jo Cox, who was murdered by a right-wing extremist days before the EU referendum in 2016.
She said: "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.
"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."
In response, Mr Johnson said: "I have to say, Mr Speaker, I've never heard such humbug in all my life."
The highly charged debate came a day after the Supreme Court ruled Mr Johnson's suspension of Parliament unlawful.
In a further sign of the deep unease felt by many Conservatives, senior Tory AM David Melding called the Commons session "one of the darkest and most destructive", describing Mr Johnson's performance, and that of Attorney General Geoffrey Cox, as "angry and obdurate".
Mr Melding, a former deputy assembly presiding officer, said on Twitter: "Intemperate language on the verge of anti-parliamentary issued forth in a vituperation [bitter and abusive language] and contempt."
"Would Churchill, Macmilllan or Mrs Thatcher have ever deprecated the principle of Parliament in this way?
"Clearly one nation liberal Toryism has no hold on the government.
"Yesterday we needed a PM with a generous heart and the courage to reach out and unify.
"This he chose quite deliberately not to do. Instead he said the Supreme Court was wrong and Parliament was betraying the national interest."
"Truly these are dangerous times," the South Wales Central AM added.
Speaking to BBC Radio Wales Breakfast with Claire Summers, David Davies MP defended Mr Johnson.
"I thought that Labour were wrong to raise Jo Cox's name in connection with this debate and I felt they were trying to use her brutal and disgraceful murder as a means to try and shut down debate some time afterwards about Brexit," he said.
"I thought Boris was right... Conservative MPs do face a huge amount of abuse, sometimes from masked protestors, and we don't need to be told about the importance of the use of language by Labour."
First Minister and Welsh Labour leader Mark Drakeford accused the prime minister of "deliberately stoking the politics of division" in "our already deeply divided country".
"He must stop being a cheerleader for a minority and put the country first," he said.
But Montgomeryshire Conservative MP Glyn Davies said Mr Johnson had been up against a "ferocious baying mob" from the moment he entered the House of Commons.
"When the prime minister walked in he was facing 300 people on the other side that really were shouting all kinds of abuse and I think it creates an environment where you can't have sensible debate," he told the BBC news channel.
On Wednesday night Labour's Cardiff North MP Anna McMorrin tweeted: "I can barely find words to express my horror at Johnson's behaviour tonight.
"I told the house I am embarrassed to be an MP today. And I am.
"His language incites violence. He shows no sign of contrition or humility and he continues to encourage division. He must go."
Labour MP for Gower Tonia Antoniazzi also wrote on Twitter: "This evening I came home early and cried, I still am."
Opening Thursday's session, 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".