Pressure on Corbyn to resign has continued to intensify as he faces fresh resignations from the front bench – including one MP appointed to the shadow cabinet just two days ago.

During Prime Minister’s Questions on Wednesday, Cameron waded into Labour’s misery, criticising Corbyn’s role in the EU referendum campaign.

“It might be in my party’s interest for him to sit there, [but] it’s not in the national interest and I would say, for heaven’s sake man, go,” he said.

Corbyn’s arrival in the Commons chamber was met by stony silence from his backbenchers.

As he took to the Despatch Box, many Labour MPs sat with their arms crossed.

The Labour leader used PMQs to challenge Cameron over “disgraceful” levels of child poverty and said the referendum result had been a rejection of the status quo.

Cameron hit back: “Of course we need to do more to tackle poverty, we need to do more to spread wealth and opportunity, but to try and pretend that last Thursday’s vote was a result of the state of the British economy is complete nonsense.

“We all have to reflect on our role in the referendum campaign,” he added. “I know he says he put his back into it. All I would say is I would hate to see him when he is not trying.”

Former acting Labour leaders Harriet Harman and Margaret Beckett have called on Corbyn to fall on his sword.

It has been reported that an MP from Britain’s opposition Labour Party, Angela Eagle, is set to announce that she will bid for the leadership of the party amid the revolt against Corbyn.

Eagle, a former pensions minister, quit as Labour’s top business official on Tuesday, one of more than 20 people to resign from Corbyn’s opposition policy team.

The latest Labour frontbench resignation came from MP Pat Glass, who announced she was quitting the education brief she was given after the mass frontbench walkout, saying the situation was “untenable”.

Momentum, the grassroots movement that mobilises in support of Corbyn, said it was postponing a rally planned for Wednesday night “due to overwhelming demand”. The Labour leader had been due to address the event.

Shadow chancellor John McDonnell called on the party’s MPs to “play by the rules”.

“It looks as though we will have a leadership election,” he told Sky News

“All we are saying to Labour MPs is, play by the rules of our party and, if there is to be a democratic election, respect the decisions of our members.”

Harman said Corbyn had “no right or mandate” to stay in office.

Meanwhile, Prime Minister Cameron says his successor could begin negotiations with the European Union about the country’s exit from the bloc before the formal Article 50 legal process is triggered, despite comments from the EU to the contrary.

“They have said ‘no negotiation, without notification’ but I don’t think that excludes discussion that a new prime minister can have with partners or indeed with the institutions so that we continue to get off on the right foot,” he said.

Cameron also said that keeping the United Kingdom together was of paramount importance, responding to concerns that its constituent nations could seek independence after Britons voted to leave the European Union.

“Keeping the United Kingdom together is an absolute paramount national interest for our country,” he told parliament

He warned that Britain faces troubled economic times after it voted last week to leave the European Union, but said the Government would not abandon its rules on limiting public spending.

“There’s no doubt in my mind these are going to be difficult economic times,” Cameron told parliament on Wednesday.

“If we do see economic difficulties, one of the ways we have to react to that is to make sure that our public finances and economy remain strong … so I don’t think it would be right to suspend the fiscal rules,” he said, rejecting a call from Corbyn for more investment.