Britain's Jews are more frightened and insecure than they have been in this country in many decades after an upsurge in antisemitic violence linked to the conflict between Israel and Hamas, community leaders say.

Latest figures from the Community Security Trust showed that antisemitic incidents are up 36 per cent since January. The figures do not include the doubling of attacks in recent weeks.

Incidents being investigated by police include an attack on a rabbi in Gateshead, bricks thrown through a Belfast synagogue windows, a group of Asian men who shouted "Heil Hitler" as they drove through a Jewish area in Manchester and a man who tweeted that an area of London should be bombed so "Jews feel the pain".

In London's Tower Hamlets, near the scene of the 1936 Battle of Cable Street between fascists and their opponents, a journalist who went to photograph a black jihadist flag this week was told: "F*** off Jew."

In other areas of London, pro-Hitler banners have been waved during marches supporting the Palestinian cause.

In Liverpool, people entering a synagogue have been attacked with chants of called "baby killers" .

France has seen some of the worst incidents. Just days ago, firebombs were thrown at a Jewish community centre in Toulouse after a pro-Palestinian demonstration. Paris has now banned all pro-Palestinian demos in an attempt to stem the antisemitic hatred.

The recent upsurge is all the more pointed because it comes just as Jewish ex-servicemen joined hundreds of people at London's Bevis Marks synagogue to remember those who fought in the Great War.

Jeffrey Fox, chairman of the Association of Jewish Ex-Servicemen and Women, said: "For years, this association has fought against anti-Semitism in all its forms. In recent years we have welcomed the fact that it was no longer as serious an issue in this country. However, recently we have been alerted to the fact that while it has been dormant for some time, it is apparently very much alive.

"There have been attacks on synagogues and Jewish institutions which are reminiscent of the 1930s. We call upon right-thinking members of the public to express their horror - and disassociation - with attacks on their fellow citizens merely because of their faith and beliefs."

Rabbi Dr Jonathan Romain of Maidenhead synagogue said: "Many of us have been astonished at how feelings against Israel, which are perfectly legitimate to hold, have so easily rolled over into antipathy to Jews, which is both unjust and racist. This has been evident in speeches or protest marches attacking Jews. But why? Those who dislike Chinese policy in Tibet do not protest outside Chinese restaurants in London or Bradford, yet they blame British Jews for what is happening in Gaza.

"Not only is this extremely hurtful, it leaves the question of whether it is due to ignorance or is deliberate. If it is the latter, then it would suggest that the sentiment 'anti-Semitism is a light sleeper' is sadly true."

The Council of Christians and Jews said: "The news from Israel and Gaza continues to shock and horrify, and we renew our prayers for a breakthrough to end the death and destruction. Of concern also is the escalation of physical violence and verbal assaults directed against Jewish people and property around Europe. Reports in the media highlight the fear of Jews in Britain, irrespective of their views on the conflict, who are being targeted by ignorant and malicious people. We call upon those of all faiths and none to stand up against racism and antisemitism wherever it occurs."

Jonathan Arkush, vice-president of the Board of Deputies, said: "There seems to be an avalanche of hostility to Israel which has morphed into anti-Semitism."

He said too many politicians were rushing to judgement. "There is a direct link between politicians saying things and people then being emboldened to go and attack Jews. There is this constant drumbeat of anti-Israeli agitation that is causing British Jews to be more worried more insecure than at any time I have ever known."

The Community Security Trust recorded 304 antisemitic incidents across the United Kingdom in the first six months of 2014. This is an increase of 36 per cent from the 223 incidents recorded in the first six months of 2013.

The highest monthly total was 62 antisemitic incidents recorded in June 2014, and the lowest was 39 in March. The increase was felt across the UK, with rises in London, Manchester, Hertfordshire and Leeds.

Of the 304 incidents reported to the trust during the first six months of 2014, 69, or 23 per cent, showed evidence of political motivation. Of these, 52 incidents showed evidence of far right motivation, 15 showed evidence of anti-Zionist motivation and two showed evidence of Islamist motivation.