SHADOW Chancellor John McDonnell has launched a ferocious attack on a “small group” of opponents of Jeremy Corbyn who he accused of trying to “destroy” the Labour Party in order to oust the leader.

McDonnell hit out as Labour’s leadership contest threatened to descend into internecine warfare, with Corbyn’s detractors ramping up allegations of bullying, intimidation and abuse, which they said they the leadership had failed to condemn.

Former shadow minister Seema Malhotra disclosed she had lodged a formal complaint with the Commons Speaker John Bercow after claiming that staff working for Corbyn and McDonnell entered her Westminster office without permission.

Leadership challenger Owen Smith said the party was on “its knees” and could split if Corbyn remained at the helm, as the former shadow work and pensions secretary sought to harden his pitch to replace him.

However, McDonnell, who is Corbyn’s closest ally, challenged critics of the leadership to confront them directly and not to “pick on” staff who he said were not in a position to defend themselves.

McDonnell also appealed for an end to what he suggested were unfounded allegations, which included claims in a letter signed by more than 40 women Labour MPs that that Corbyn has failed to do enough to stamp out “intolerance and misogyny”.

Speaking on the BBC’s Andrew Marr Show, McDonnell looked directly into the camera to make his appeal for unity as he called for an end to claims from anti-Corbyn groups such as Saving Labour that the party could split.

“Let me just say this to Labour Party supporters, Labour Party members, members of the Parliamentary Labour Party — we’ve got to stop this now.

“We have got to stop this now. There is a small group out there that are willing to destroy our party just to remove Jeremy Corbyn. We have got to stop them,” he said.

“In addition to that, last week Save Labour were talking about splitting the party.

“I want Owen (Smith) and Jeremy and everybody to say ‘let’s stop this now.”

Malhotra, who was one of a number of MPs who quit Corbyn’s shadow cabinet resignation en masse, said the unauthorised entry by staff into her office constituted a serious breach of parliamentary privilege.

“The implications of this are extremely serious. This is a breach of parliamentary privilege and is a violation of the privacy, security and confidentiality of a member of parliament’s office,” she said.

However, McDonnell said the office manager concerned had simply been checking whether Malhotra had moved out of the office after quitting as shadow chief Treasury secretary last month in protest at Corbyn’s leadership.

“I have now got a member of staff — she’s a widow with daughters, this is her sole income — she’s now worried she’s going to lose her job and face prosecution because it’s described as a break-in. That’s just so distressing, it’s unacceptable. This has obviously been an error,” he said.

But in a plea aimed at curbing feuding within Labour’s ranks, McDonnell acknowledged that there would have to be some form of mediation once the current leadership contest is over.

However, leadership rival Smith said that if Corbyn was re-elected as in September, that it could spell the end for Labour as a serious political force.

“My grave worry is that the party might split apart, that having been a great force for good in Britain for a hundred years and more we could cease to be that,” Smith told Sky News’s Murnaghan programme.

“We are not looking at the moment like a government-in-waiting. We don’t look like a credible powerful opposition, one that people could imagine running the country. I think that’s what we’ve got to be.

“It’s time for Labour to really get up off its knees and start fighting back against the Tories. I know that’s what Jeremy wants too but I’m not sure he can do that.”

Meanwhile, Malhotra’s replacement as shadow chief secretary, Rebecca Long-Bailey, told Sky News that staff had been planning to swap their offices and thought her predecessor had already vacated hers.

She added: “Unfortunately there has been a bit of miscommunication and misunderstanding on both sides.”