Shadow chancellor John McDonnell has said the Labour leadership is ready to address issues which have led eight of the party’s MPs to switch to the new Independent Group in Parliament.

Mr McDonnell acknowledged that criticisms raised by Labour MPs such as Ian Austin were “valid” and urged anyone considering resignation to stay in the party and help “hold the family together”.

He said Labour had not been “severe enough” in dealing with complaints of anti-Semitism and he wanted to see tougher sanctions, including a lifetime ban from membership.

He said there would be an “appropriate sanction” if complaints were upheld against former Militant leader Derek Hatton, who was suspended from the party two days after being readmitted following a 33-year exclusion.

Following the first resignations on Monday, Mr McDonnell promised a “mammoth listening exercise” to address criticisms.

Speaking to the Press Association during a visit to Willenhall in the West Midlands, he said: “What we’ll do now is listen to the criticisms of those who’ve left. Of course we will, and we’ll deal with them.

“That’s what unfortunate, because if they’d have stayed they could have helped us deal with them, but that door now closes.”

Dudley North MP Ian Austin, a long-time critic of Jeremy Corbyn’s handling of anti-Semitism complaints, has said he is considering “very carefully” whether to follow his former colleagues out of the party.

Mr McDonnell said: “If Ian Austin is considering leaving, my message to him is, ‘Don’t go, stay with us, you’ve raised valid concerns, you can help us sort this out’.”

The shadow chancellor said he was “happy” to meet Mr Austin to discuss his concerns.

“I’m happy to meet whoever, and I’ve been meeting the last couple of days large numbers of Labour MPs – individuals and in groups – talking it through,” he said.

He said he thought there “might be a couple” of other Labour MPs considering defection, but insisted: “We can sort out the problems that they’ve raised.

“I think we’re a family, the Labour Party is a family. We’ll hold the family together and we’ll be effective in terms of our opposition to the Tories’ Brexit deal, which will destroy our economy.”

Asked if there was a “way back” for MPs who quit the party, he replied: “There’s always a possible way back, course there is.

“I was brought up in the Catholic tradition. I’m a great believer in the powers of persuasion.”

Addressing concerns about the handling of anti-Semitism complaints, Mr McDonnell said: “We’ve got to deal with it. We haven’t been quick enough, I don’t think we’ve been severe enough.

“We’re going to look at sanctions – they haven’t been hard enough and individual MPs have raised cases where the sanction hasn’t fitted the crime. So what we need to do is make sure those sanctions are severe enough.

“My view (is) if there is someone who is an anti-Semite and is regularly offending, they should be not just barred from the party, but barred for life.”

Mr Hatton was suspended on Wednesday pending an investigation into a 2012 tweet which allegedly implied that every Jew was responsible for the actions of the Israeli government – something which is explicitly covered in the international definition of anti-Semitism adopted by Labour last year.

Asked about the former Liverpool council leader’s readmission to the party, Mr McDonnell said: “Anyone can apply for the Labour Party and goes through the normal process, that’s what he’s done.

“The one thing that prevents you even having your application considered is if you stood for another political party, and he hasn’t for a number of years.

“So he’s come through, there’s been a complaint come in … that’ll be investigated and there’ll be an appropriate sanction

“But, again, I just repeat, we do not want anti-Semites in our party. Full stop.”