An American rabbi will join an extreme right-wing anti-Islamic-fundamentalist group in a protest outside the Israeli Embassy in London next week.
Rabbi Nachum Shifren, from California, said he was supporting the English Defence League because he opposed multiculturalism, and promised to act with "full force" against shariah law.
But his plans have been roundly criticised by Jewish community organisations. The Community Security Trust said that Jews who believed they could shape the EDL, or find shelter in the group, were "utterly deluded".
Board of Deputies chief executive Jon Benjamin said: "Rabbi Shifren displays breathtaking naivety and ignorance in associating himself with the EDL and in the way he characterises the British Jewish community.
"Whatever the dangers of radicalisation in the UK, they apply just as much to the right as to the left and to Islamism."
Mark Gardner, Community Security Trust communications director, said: "The EDL's Jewish branch is a tiny part of a far larger movement, dominated by white males who would previously have made up National Front marches and English football hooligan gangs.
"EDL actions are violent and intimidatory, attacking police and random Asians. Any Jews thinking that they can shape such dangerous forces and find shelter there are utterly deluded."
Los Angeles-based Rabbi Shifren said: "I am coming to the UK to express my solidarity with the patriots in England who are on the front line in the war on jihad and stealth jihad.
"Multiculturalists have brought us to the brink, insisting on degrading our own cultures while pandering to forces of darkness that threaten to completely transform our societal foundations."
Rabbi Shifren said the "enemies" of Western democracies had sought to destroy religious foundations, loosen patriotic bonds and were responsible for a "wave of Middle Age darkness in the Muslim religion".
"It is my goal to create a united front of American/British patriots that will act with full force against shariah law and any attempt to accommodate it either through legislation or by 'compliant' economic policies."
An ex-lifeguard, known as "the surfing rabbi", Rabbi Shifren previously worked as a fitness trainer for Israeli paratroopers and a driver for assassinated extremist Rabbi Meir Kahane. In March 1993 he was thrown out of a Conservative rabbis' conference for heckling Jesse Jackson.
He is standing for election to the Caliifornia state senate in next month's mid-term elections.
Charedi leader Rabbi Avraham Pinter said Rabbi Shifren did not accurately represent the Jewish community: "I am concerned about the visit. He should mind his own business.
"It's highly irresponsible to describe him as a 'senior rabbi' as the Observer did at the weekend. He will come and go and no one will take any notice."
The EDL is also said to have developed links with anti-jihad groups in the American Tea Party movement. Rabbi Shifren is a regular speaker at Tea Party conventions and said he is "completely supportive" of the movement, which attacks big government and high taxes, and has a growing anti-Islamic wing.
Pamela Geller, the executive director of the Stop Islamisation of America organisation, is also thought to be working with the EDL following her campaign against plans to build an Islamic cultural centre near Ground Zero in New York.
Last Saturday more than a dozen people were arrested after around 1,000 EDL supporters clashed with police during a protest in Leicester.
Officers were pelted with smoke bombs, bricks, coins, bottles and cans.
Dozens of videos posted on YouTube this week show the extent of the violence, including an incident where a group of EDL members smash their way into a restaurant in an attempt to attack a woman.
The EDL is planning to hold its pro-Israel event outside the Israeli embassy in London on October 24. The plan was greeted with horror by the embassy. Its spokesman said: "We wish to disassociate ourselves from next Sunday's event, and from any attempts to link Israel to the EDL."
Brazilian-born Jewish activist Roberta Moore is head of the EDL Jewish division which was set up earlier this year.
She said: "We are going to the embassy to show support for Israel, to fight jihad in our streets. It just cannot go on. We do not have enough Jews standing up to protest.
"Rabbi Shifren contacted us and we invited him to come and speak."
She claimed the Jewish division has around 100 members, most of whom are Jewish.
"We are causing ripples everywhere because we are achieving things the Jewish community has not. CST and the Board of Deputies speak out but their voices are not heard. People want to see action on their streets.
"Our members are not hooligans. We are educated people with jobs. If we defend ourselves is that hooliganism? The Jewish community sit in their houses and do nothing. They will enjoy the benefits of our action."