Antisemitic incidents across Britain increased by 11 per cent in the first six months of this year, with a shocking 62 per cent rise in London.
Figures published in a report by the Community Security Trust show that between January and the end of June there were 557 reported incidents, up from 500 in the first six months of 2015.
While London witnessed 379 incidents - up from 234 - in Manchester there was a sharp decline, with 62 reported cases representing a 54 per cent fall on the same period last year.
A quarter of nationwide incidents occurred on social media sites, which are now regarded as "an essential tool" in the repertoire of antisemites, according to CST.
Amber Rudd, Home Secretary, said: "I condemn the deplorable rise in antisemitic hate incidents, and will continue to work with law enforcement partners and with the Jewish community to ensure their safety and security."
Key facts
Overall increase in first six months of 2016 - 11%
Total number of incidents across the UK - 557
Number of incidents in borough of Barnet - 117
David Delew, CST's chief executive, said the rise "comes at a time when division, intolerance and prejudice appear to be deepening within our society.
"Reversing this worrying trend requires real leadership from all political parties, and for the social media companies to take their share of the responsibility."
The half-yearly figures were the worst set of numbers since 2009 and the fallout from Israel's Cast Lead operation in Gaza.
Although there was no spike in Middle East violence to trigger this year's increase, CST said the months of May (125 incidents) and June (112 incidents) were respectively the fourth and sixth worst since records began in 1984.
The charity was cautious about attributing the direct causes, but said the atmosphere earlier this year had been a contributory factor.
April to June saw "sustained public debate about antisemitism, particularly in relation to the Labour Party, and about racism and extremism more generally," the report said.
"It was also a period when some Jewish public figures, including politicians and student activists, were the targets of sustained campaigns of antisemitic threats, abuse and harassment on social media.
"It is possible that a combination of these factors, rather than a single trigger event, contributed to an overall increase in the number of antisemitic incidents."
Andy Burnham, Labour's Shadow Home Secretary, said the increase was "worrying".
"Labour will always lead the way in tackling any form of hatred or prejudice, but we are being hampered in that fight by a small number who are not welcome in our party," he said.
CST said it was unusual to see such a difference between London and Manchester - home to the largest Jewishcommunities in Britain. There was "no obvious explanation for these opposing trends", the report said.
The rate of the rise was similar across all London boroughs with the most sizeable Jewish communities.
There were 117 incidents recorded in Barnet, the borough with the largest Jewish population in the country; 40 in Hackney; 35 in Camden; 31 in Haringey; 28 in Westminster; and 20 in Redbridge.
CST said the work of the Shomrim volunteer community security group in Stamford Hill and areas in north-west London had been effective in tackling antisemitism, but remained one "small factor" and was not responsible for the "substantial" increase in incidents being reported.
The Manchester figure could be partly attributed to a decrease in tension after two years blighted by the protests outside the Israeli-owned Kedem store in the city centre.
The report details how almost 200 incidents were "random" in their nature. These included abuse of noticeably Jewish members of the public. Abusive behaviour accounted for the most incidents (431) in any category.
There were more than 40 violent assaults, a similar number of general threats, as well as attacks on property and the circulating of antisemitic literature and other material.
A slight rise in incidents targeting synagogues was recorded, and Jew-hate on campuses more than doubled. CST recorded 27 incidents affecting Jewish students or academics, compared to 11 in the same period last year.
In cases where victims reported details of their abuser, the perpetrators came from a mixture of backgrounds, including white Europeans, black people, Asians and Arabs.
Around 80 per cent of the incidents were carried out by adults, and 20 per cent by children. Eight out of 10 were perpetrated by men, with women accounting for around 12 per cent of incidents.
The apparent motivation for antisemitic episodes was provided in less than half the cases, but included far-right motives, references to Zionism and the Middle East, and Islamist discourse.
The figures pre-date the fallout from the EU referendum and the general rise in hate crime around the country. The JC understands that there has not been a significant increase in antisemitic activity related to the Brexit vote.
A Shomrim spokesman said: "There haven't been any significant incidents like we saw the previous year when there was organised antisemitic incidents and demonstrations.
"But there are regular, isolated incidents. They can be a neighbour getting angry and having a go in an antisemitic way. People used to ignore it much more and not do anything. But now the community has got more confident in the justice system and that the police will take a report seriously.
"Most incidents we deal with get reported to the Metropolitan Police."
Jonny Wineberg, chairman of the Manchester Jewish Representative Council, said the drop in incidents in the city was welcome.
"It's good news that there were fewer incidents. There has been a massive amount of work to foster community cohesion.We hope that's having an effect."
But Mr Wineberg warned that antisemitism in the north-west of England remained "very high".
"Any one incident is too many. These results encourage us to do even more. We are not complacent."
