The strictly Orthodox community is facing a rise in child poverty as a result of benefit cuts and lack of secular education for boys in its schools, according to a new report.
With the economic downturn and government spending cuts, it says: "The alarm bells should be ringing loudly".
The report, by Jonathan Boyd, executive director of the Institute for Jewish Policy Research (JPR), is the most comprehensive survey of child deprivation undertaken in modern British Jewry.
The Charedi community is particularly at risk of "considerable damage".
"The potentially toxic mix of a paucity of professional skills, more mouths to feed, a reduction in government support and a likely diminution of charitable donations all point towards the probability of a noteworthy increase in child poverty and deprivation cases in the coming years," it says.
The poverty level is difficult to calculate because of a lack of data on incomes. But information from the 2001 census and other reports give some indication of its extent. Around eight per cent of UK Jewish children - 3,800 - live in overcrowding, a third of them in the London borough of Hackney, home to the largest Charedi community.
Nearly nine per cent of children, over 4,300, live in households with no adult in work. Another 4,000 live in low-earning households. Around one in six is eligible for free school meals in the strictly Orthodox Pardes House Primary school in Barnet and in the pluralist Clore Tikvah Primary in Redbridge, Essex. Almost one in ten are on free school meals at JFS.
While outside the Charedi community, the numbers of poor Jewish children are "low", some deprivation exists in Redbridge and other areas. More than one in ten Jewish children live in single-parent households in Redbridge.
Financial hardship can hit synagogue membership and participation in youth programmes, the report warns.
It also notes that the cost of maintaining a religious lifestyle can impose an additional burden. Some people are plunged into debt by spending more than they can afford on simchahs to keep up appearances.
The cap in housing benefit and rising rents are likely to create further difficulties. A study nine years ago revealed that more than one in eight Hackney families could not afford to give their children a meat, fish or vegetarian meal at least twice a week.
JPR researchers expect that the 2011 census will record an increase in child deprivation. One problem is that Charedi boys are "schooled so heavily in Jewish studies" that they leave school without the secular qualifications that can lead to higher-paid jobs. But the report says that changes to the school curriculum can only come with the approval of the strictly Orthodox rabbinate.
In the meantime, it suggests new training vocational schemes, tailor-made to strictly Orthodox young men, which can provide them with better employment prospects.
It notes a "remarkable" number of charity and volunteer schemes within the Charedi community particularly, and an "extraordinary" range in general, to help people in need.
A group of donors in Edgware spends an estimated £20,000 a year supplying challah, wine and chickens to struggling families.
But the report says these efforts are geared largely towards ameliorating rather than preventing poverty.
In the current economic climate, the ability of Jewish welfare organisations even to maintain existing services, will be severely tested, according to the report. It suggests a new volunteer programme for gap-year students to do work for Jewish charities home similar to schemes for them in Israel.