The danger to long-term survival is, quite simply, the modern world, in which rising living standards and the growth of individualism have caused the collapse of traditional communities.
For the country's gentiles the situation is bad enough, with the current widespread anxiety over family values. But for Anglo-Jewry, the signs are even more alarming. Since the 1950s its numbers have declined from 450,000 to fewer than 300,000, a loss of 10 Jews a day.
Its leaders are so alarmed at what they see as a drift towards secularism, and the dwindling number of traditional Jewish weddings, that they have decided to act.
A new charity, Jewish Continuity, which hopes to preserve and foster the community's religion, culture and language, has been set up.
It has the controversial brief of preserving Jewish traditions by 'intensifying ethnicity' through educational and cultural projects.
Backed by donations from wealthy Jews, it has just approved grants totalling pounds 250,000 for initiatives ranging from family-based Hebrew reading schemes to help for Jewish children to receive 'positive Jewish experiences' to extend their knowledge of Judaism and Jewish culture.
The charity was inspired by the Chief Rabbi, Dr Jonathan Sacks, who has voiced his concerns about the gradual secularisation of British Jews.
The drop in the number of synagogue weddings - falling from around 1,500 a year in the late 1970s to fewer than 1,000 today - has alarmed the Jewish establishment. There has been an accompanying rise in the number of Jews 'marrying out', with one in three British Jews getting married now preferring mixed-faith marriages. The proportion is expected to rise to more than half within five years.
Clive Lawton, the chief executive of Jewish Continuity, puts the situation in stark terms: 'The catastrophic thing for the Jewish community is that if you don't marry Jews you can't create Jewish community.'
The charity is currently studying how to encourage traditional synagogue weddings. It also hopes to set up dating agencies for young Jews.
They would be based on a marriage bureau, Connect, set up 10 years ago by the Jewish Marriage Council, which brings about introductions by inviting young Jews to submit their details anonymously for distribution in a bulletin.
The scheme has proved successful but has had to overcome the stigma of being seen as a 'lonely hearts' club magazine.
Mr Lawton, however, believes dating agencies have potential.
'We do not disagree with the concept that marriages are made in heaven, but we do believe we have got to give God a chance and help him out. It is not a Jewish tradition to believe in miracles.'Reuse content