Last Thursday the Labour MP for Bermondsey and Old Southwark, Neil Coyle, was knocking on doors, trying to reassure local residents about their safety. The evening before, a young man had been stabbed to death and two others taken to hospital after a series of knife attacks in and around his south London constituency.

A police cordon had been thrown around the crime scene in Warham Street, Camberwell – an area where people have become all too familiar with violence and the loss of young lives in recent times. In May this year, 17-year-old Rhyhiem Ainsworth Barton was shot dead on the same street. Coyle and local residents were shocked and angry.

Since 2010, the period over which Theresa May has served as home secretary and prime minister, the number of police officers and police community support officers (PCSOs) in Southwark has fallen by 400. Violent crime has risen and prosecutions have slumped. Local authority budgets have been cut to the bone, as have local services.

“We should be absolutely roasting the Tories, and particularly the prime minister, on their record on violent crime – and how they can have allowed this to happen,” Coyle said. “Sadly, in three years as an MP, I have met the mothers of murdered young men and teenagers who fear they’ll never see justice as killers get away with murder under a government that has hacked police numbers and overseen disastrous prosecution figures.” For many Labour MPs and activists these are the issues they want their party to focus on in order to dislodge the Tories from power.

Instead, the past week has seen Labour monopolise the headlines for all the wrong reasons. The only issue on which it has made waves is the interminable and increasingly tortuous row over antisemitism in its own ranks, and the resulting near-total breakdown in its relations with the British Jewish community. Everyone – from people in Jeremy Corbyn’s office to activists in the field – is frustrated. “Somehow we have managed to become the story for the August silly season,” said one party moderate. “The problem is that this is not a normal silly-season story. This one will not just come and go. It is completely incendiary and hugely damaging in the longer term.”

Facebook Twitter Pinterest MP Margaret Hodge is facing disciplinary action after telling Corbyn he was an antisemite. Photograph: Yui Mok/PA

A year ago, Corbyn radiated a post-Glastonbury confidence. The left of the party was united behind him and the grassroots pro-Corbyn movement, Momentum, was still growing in size and influence. Corbyn’s critics had been silenced. Now, however, splits have opened on the left, and inside Momentum, over the handling of the antisemitism issue. Tensions between the parliamentary party and the leadership have resurfaced. Two MPs, Margaret Hodge and Ian Austin, who both lost family members in the Holocaust, are facing disciplinary action by their own party for criticising the leadership over its stance on, of all issues, antisemitism.

Meanwhile, young party members who joined up on Corbyn’s promise that they would be given a say over policy are beginning to demand just that. They are questioning the way the leadership is behaving not just on antisemitism, but on other key issues including Brexit, and want to see the democracy that the leader spoke of delivered soon.

As the Corbyn halo has slipped, people are speaking out once more. Above all, the majority want their party to take a long hard look at itself and get back to the programme – that of ousting the Tories. Emily Wallace, chair of the Labour party in Vauxhall, south London, is appalled by the factionalism and infighting she sees almost daily. “I am a long-term political activist, I love the Labour party, but right now I want to pick it up and shake it to its senses,” she says.

Arguments inside Labour about antisemitism have been simmering ever since Corbyn became leader in 2015. No one can dispute that he has spent much of his career fighting racism but, as a long-term and ardent critic of Israel’s policies and staunch supporter of Palestinian causes, he has always been distrusted by the Jewish community. Corbyn supporters say criticism of him for things he has said and people he has shared stages with in the past has been deliberately misrepresented by the disaffected old Blairite right of the party, egged on by some Jewish Labour supporters.

The whole issue of Corbyn versus the Jewish community has long had the potential to blow up in his face and that is what it is now doing.

For much of the early part of his leadership, the tensions centred on how robustly the party was dealing with alleged antisemitism among its members.

The most celebrated case was that of former London mayor and Corbyn ally Ken Livingstone, whose controversial remarks about Hitler and Zionism appalled the Jewish community and Israeli government alike. For well over a year the party refused calls to expel Livingstone and instead suspended him while dithering over its investigations, until Livingstone resigned his membership this May. Dozens of other inquiries into allegations of antisemitism against other Labour members seemed stuck in an appallingly inefficient process, creating an impression of paralysis. Jewish leaders saw it as deliberate stalling and evidence that Corbyn was not willing to crack the whip.

Then, last month, the argument reached a new level when the party’s national executive committee (NEC) decided how it would rewrite the party’s rule book and define antisemitism. Hugely controversially, it stopped short of endorsing the full International Holocaust Remembrance Alliance (IHRA) definition with all its examples. The party argued that under one of the IHRA’s examples, criticism of Israel could be deemed antisemitic. There was uproar in the parliamentary party and the Jewish community, as the IHRA definition is widely accepted in other countries and by more than 130 councils in the UK.

Facebook Twitter Pinterest Ken Livingstone left the party in May after a drawn-out investigation into his remarks about Zionism. Photograph: Peter MacDiarmid/Rex/Shutterstock

Suddenly an awkward issue for Corbyn was elevated into the biggest crisis of his leadership. Day after day during the last fortnight more stories have been dug up from his past, including one last week about him taking part in an event in 2010 where the actions of Israel in Gaza were compared to the Nazis.

As pressure on him grew, Corbyn apologised for concern caused and acknowledged he had on occasions appeared with people “whose views I completely reject”. The three largest Jewish newspapers – the Jewish Chronicle, Jewish News and Jewish Telegraph – tore into him, creating identical front pages saying a Corbyn government represented an “existential threat to Jewish life in this country”.

In the midst of it all, Hodge told Corbyn he was an antisemite and Austin had a furious exchange with Ian Lavery, the party chairman. Both are now subject to internal investigations that they say have been instituted with a haste absent in all investigations into cases of alleged antisemitism. Then last week the Jewish Chronicle produced a recording of one of Corbyn’s allies, Peter Willsman, telling the NEC meeting at which the new definition was discussed that Jewish “Trump fanatics” were “making up” a lot of the antisemitism allegations. Willsman, who is on the NEC dispute panel that investigates complaints against members, asked people to raise their hands if they had ever seen examples of antisemitism in Labour, adding: “I’ve certainly never seen any.”

Unity was blown apart on the left. Momentum, whose founder Jon Lansman is Jewish, withdrew Willsman’s name from its slate of candidates for the current round of NEC elections, a decision that drew fury from other senior members, including Matt Wrack, who told the Guardian: “With this decision to drop Pete Willsman, the leadership of Momentum has bottled it. It is as if they have never gone to a political meeting before and heard someone rant about a subject.” Deputy leader Tom Watson tweeted: “For the avoidance of doubt: Peter Willsman is and always has been a loud mouthed bully. He disgusts me.”

On Friday Corbyn wrote an article in the Guardian saying antisemites had no place his party. It was well received by some, but senior figures in the Jewish community were unimpressed and said they believed it was timed deliberately to coincide with the Sabbath so they could not give an official response.

Facebook Twitter Pinterest The joint campaign front pages of the Jewish Telegraph, Jewish Chronicle and Jewish News. Composite: Various

Now Watson is calling on the leadership to immediately lift investigations into Hodge and Austin and adopt the IHRA definition in full. If it does not, he says, Labour will “disappear into a vortex of eternal shame and embarrassment”.

The short-term danger Watson and others see is that all this will carry on through the summer and into the party conference season, doing untold damage. The fears are well founded: Labour MPs and peers will both hold votes next month at which they are expected to defy the NEC and Corbyn by adopting the full IHRA definition into their own rule books, as opposed to that of the party at large. But any decision to do so has first to be approved by both the NEC and the party conference.

An almighty constitutional clash looms, as well as a row over who will pull strings for Corbyn at key moments. Among those on the right of the party, there is deep concern that Willsman, a key vote fixer on the left, will still be on the NEC throughout the conference season, doing deals. Richard Angell, director of the Progress pressure group, says Corbyn and his team are not pushing for the removal of Willsman from the NEC because they want him to deliver votes at conference and avoid defeats for the leadership on Brexit, the democracy review, and, potentially, antisemitism.

There are also signs of frustration among younger members who believed their party under Corbyn would be genuinely open and flexible. New groups are forming and attracting new members. One is Open Labour, run by Tom Miller, a Labour councillor in Brent. It now has more than 3,000 supporters.

Miller says: “If Labour is to live up to the promise of democratic renewal, we need to tackle issues like antisemitism to show that all members can feel safe and supported. We need open debate on topics like Europe: Labour’s democracy is especially important when the topics are hardest.” Only then will Labour be able to reunite and focus on the policies it needs to win a general election.