John Bercow pleaded with MPs on all sides to tackle the “toxic” political culture as the fallout continued from Boris Johnson’s combative Commons performance.
The Commons Speaker said the House “did itself no credit” in the angry exchanges which followed the Prime Minister’s statement on Wednesday night.
As MPs returned to the Commons on Thursday, Mr Bercow said: “There was an atmosphere in the chamber worse than any I’ve known in my 22 years in the House.
“On both sides passions were inflamed, angry words uttered, the culture was toxic.”
He told them to “lower the decibel level and to try to treat each other as opponents, not as enemies”.
Mr Johnson provoked a furious response by telling MPs they should honour the memory of murdered parliamentarian Jo Cox by delivering Brexit.
There was uproar in the Commons as the Prime Minister repeatedly berated MPs, rejected calls to temper his language and said the best way to honour Mrs Cox – an ardent Remainer – was to “get Brexit done”.
He addressed Tory MPs at the 1922 Committee on Thursday but refused to answer journalists’ questions on whether he would apologise for his language choices as he left the meeting.
However a senior Conservative told PA that the PM had “clarified” his words when he spoke to the backbenchers.
Secretary of State for Digital, Culture, Media and Sport Nicky Morgan appeared to acknowledge concerns about Mr Johnson’s use of language, particularly in the context of threats of violence against politicians.
“But at a time of strong feelings we all need to remind ourselves of the effect of everything we say on those watching us,” she tweeted.
And Commons Leader Jacob Rees-Mogg said all people “had a responsibility to be mild in our language when we’re speaking in this House or outside”.
Simon Hoare, Tory chairman of the Northern Ireland select committee, said: “There’s a feeling of the morning after the night before in Parliament today.
“I think we looked over a precipice yesterday; didn’t like what we saw; and have pulled back.
“At least I hope that’s the case.”
But Tory chairman James Cleverly defended the Prime Minister and said the “deeply uncomfortable” atmosphere in politics was unlikely to be resolved until Brexit was delivered.
He told BBC Radio 4’s Today programme that opposition parties preferred to “continue the circular argument around Brexit” rather than put it to bed.
This can be de-escalated, the tempers can be taken out of this. But in order for that to happen, there needs to be a balance on both sides,” he said.
“At the moment, I don’t feel that opposition parties are genuine about trying to resolve this issue. It seems they would much prefer to continue the circular argument around Brexit rather than work together for a resolution and get it off the agenda.”
Labour leader Jeremy Corbyn will convene the latest meeting of opposition leaders in Parliament on Thursday to consider their next moves.
Mr Johnson had dismissed as “humbug” Labour MP Paula Sherriff’s claim in the Commons that like Mrs Cox, who was killed by a man with far-right sympathies just days before the 2016 referendum, many MPs faced death threats from people using the same sort of language as the Prime Minister.
Ms Sherriff told the BBC: “I believe the Prime Minister is inciting hatred towards MPs.”
Mr Corbyn said the PM’s language “was indistinguishable from the far right”, while his Liberal Democrat counterpart Jo Swinson said Mr Johnson’s comments were “a disgrace”.
“He heard the pleas of MPs, many of whom who have faced death threats, to moderate his language, and dismissed their concerns with the same callous bluster that has become his trademark,” Ms Swinson said.
Mrs Cox’s widower, Brendan Cox, said he felt “a bit sick” at the way her name was being used.
“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 on to what we have in common,” he tweeted.
Mrs Cox’s sister, Kim Leadbeater, told Sky News: “I think the Prime Minister needs to think very carefully about the language he uses.
“I think everybody has to think really carefully about the language they use.”
The European Commission also reminded politicians to be respectful in their exchanges, and warned of the consequences when such “values” are forgotten.
Chief spokeswoman Mina Andreeva told reporters: “I think respect is the key word.
“We would remind everybody that respect is a fundamental value of all our democracies and it is the responsibility of each and every politician to uphold our values, and history has shown us what happens when they are not respected.”
Despite Mr Johnson’s attacks, opposition parties again made clear they would not agree to an election until they were sure the threat of a no-deal Brexit on October 31 was off the table.
Downing Street said if opposition MPs did not take up the Prime Minister’s offer to table a no-confidence motion, the Government would take it as a mandate to press on with Brexit.
The Government will ask MPs on Thursday to agree to a three-day break for the Commons next week while the Tories hold their annual party conference in Manchester.
But amid the angry mood at Westminster, the opposition parties appear unlikely to agree, meaning Mr Johnson could be forced to rearrange his keynote speech due to be held on the final day on Wednesday.