London: A senior Labour MP has called on Conservative whips to identify party colleagues who use “vile and dehumanising language” towards Theresa May, after a weekend during which there were suggestions the prime minister should be knifed and hanged.

The Sunday Times quoted one unnamed Tory MP as saying: “The moment is coming when the knife gets heated, stuck in her front and twisted. She’ll be dead soon.”

Another said May was now entering “the killing zone”, and a third remarked: “Assassination is in the air.”

In the Mail on Sunday, another quote was that May should “bring her own noose” to a meeting of backbench Tories.

Yvette Cooper, the head of the House of Commons home affairs select committee, told BBC Radio 4’s Today programme that such language was unacceptable, particularly after the murder of the Labour MP Jo Cox in 2016.

“This is vile and dehumanising language towards a woman MP, towards a prime minister who, no matter how much you might disagree with her, is someone who is doing a job in public life,” she said.

“Nobody should be subject to that kind of violent language, which I think is normalising violence in public debate at a time when we lost Jo Cox, we have had threats against Rosie Cooper, we have had other violent death threats against women MPs.”

“It’s about time we do know who is that Conservative MP who is making these threats because maybe if they use that language they will stop doing so if they are being called out publicly from using that kind of vile and irresponsible language again.” she added.

One Tory MP and public critic of May, Mark Francois, said the language was “unacceptable” but that he would not tell the Conservative chief whip, Julian Smith, how to do his job.

He said the language was born of frustration: “The problem is that there is a lot of frustration on the backbenches at the moment, both among leavers and remainers, at the general state of play. When you try to convey that to No 10, no one is listening.”

His failure to completely condemn the language prompted criticism from two pro-remain Tory MPs.

“Mark Francois does not speak for me or vast numbers of moderate Conservative MPs,” tweeted Antoinette Sandbach. “We are fed up of seeing the ERG [European Research Group] bullying and undermining the PM because of their so called ‘vision’ of Brexit.”

Anna Soubry tweeted: “I am appalled that my colleague Mark Francois failed unequivocally to condemn the disgraceful and dangerous language used by a fellow Conservative MP against the PM.” She called it “shameful”.

Another May critic on the Tory backbenches, Andrew Bridgen, told Good Morning Britain: “At the moment that [language] is unhelpful. It won’t persuade colleagues to back a change of leadership. It’s actually going to be counterproductive at this point.”

Bridgen told LBC he still hoped May could be forced out, saying: “I think if we had a Brexiteer in charge of the negotiations, that would shake the European Union up. They desperately need a deal. We’re huge customers for EU goods.”