Former home secretary and Sheffield MP David Blunkett has described the re-election of Jeremy Corbyn as Labour leader as a 'catastrophe' for the party.
Lord Blunkett said Corbyn's decisive victory over leadership challenger Owen Smith was an 'utter disaster' that will lead to 'annihilation' in the next general election.
But Corbyn's shadow chancellor John McDonnell has described Lord Blunkett as 'completely out of touch'.
In an article for the Daily Mail, Lord Blunkett said: "For the Labour Party I love, the party I have devoted more than 50 years of my life to serving, the re-election of Jeremy Corbyn as leader is a catastrophe.
"I'm in despair at this calamitous situation. I honestly cannot see how we're going to get out of it.
"The Labour Party under Corbyn is not electable.
"I am at a loss to understand what the 313,000 members who voted for him believe they can really achieve in the next three years, and what the eventual outcome will be, other than annihilation at a general election in 2020."
But he cautioned Corbyn critics not to split the party, warning that setting up 'an alternative movement to seize the middle ground' would be 'doomed to failure'.
Lord Blunkett described those running the Momentum group which has campaigned in support of Corbyn as 'modern-day Marxists'.
"They have shown that they are completely disconnected from the broad electorate and, when that happens to a party, it ceases to be relevant.
"That’s my worst political nightmare – a Labour Party that doesn’t connect to the lives of ordinary working people.
"Much of the support for Corbyn exists on social media, in online forums such as Facebook and Twitter.
"I can appreciate that for the activists constantly parroting each others’ soundbites, it must be deeply satisfying to be surrounded by the echoes of their own voices.
"But it’s a terrible mistake to imagine that noise is the voice of the whole country.
"With the backing of Britain, Labour leaders in the past have achieved massive social changes. We did not establish the National Health Service by being a protest movement.
"We did it by uniting millions of people. And that’s what Jeremy Corbyn can never do."
Lord Blunkett added: "I joined Labour when I was 16 years old in 1963, the year The Beatles had their first No 1.
"I became the youngest member of Sheffield City Council in 1970, and I was elected leader of that council ten years later.
"My own politics were left of centre, but I was able to work with men and women with widely differing convictions because we all wanted the same thing: a Labour government.
"That’s why, as part of the National Executive, I was instrumental in fighting and expelling the Trotskyite Militant Tendency during the 1980s. Some of those people are the same ones who are steering the Momentum organisation that now backs Corbyn.
"They are incapable of seeing that Britain will never vote for Jeremy Corbyn as prime minister, when he has no concept of national security.
"He doesn’t want to fight terrorism – he can’t even bring himself to denounce Palestinian terrorists or the IRA.
"He has already said he would never push the nuclear button, and I strongly suspect he could never sanction any kind of war at all. A Britain led by this man would be vulnerable and helpless, and the electorate knows it.
"All the Twitter and Facebook slogans in the world won’t change that.
"Labour is a great party, founded by great men. I ask myself what our past leaders, visionaries such as Keir Hardie and Clement Attlee, would make of this current mess. I strain to hear their voices down the ages, and I think they would be as speechless with dismay as I am.
"Their party – my party – has been handed over to a social splinter movement that wants nothing more than the adventure of endless protest marches. And it breaks my heart."
In response to the article, Mr McDonnell told ITV1's Good Morning Britain: "David has been fairly critical of Jeremy all along, but I'm sure he will calm down.
"There is a real spirit here of people getting together and uniting and thinking that we may face a general election soon so we have to get our act together to form not just a good opposition but to get ready to go into government."
IN OTHER NEWS:
Two teenagers arrested over murder of man found on moorland near Sheffield
Masked men armed with knife wanted over garage raid in Sheffield
Sheffield 'must catch up' to European cities
SIX things we learned from Sheffield Wednesday 2 Nottingham Forest 1
Sheffield United: Appeal against Chris Basham’s red card ‘pointless’
Download The Star's mobile app now for FREE
Get all the latest Owls stats
Get all the latest Blades stats