At least two out of every five Jewish babies in the UK are born to strictly Orthodox parents - the highest proportion ever cited in official Board of Deputies statistics.
Charedi children "now comprise 40 per cent or more" of all Jewish births, compared with a third when calculated in the last Board survey published four years ago.
But Jewish religious marriages in the UK have dropped to the lowest total on record - 836 in the year 2010 - since records began in 1901.
Over the past 30 years, marriages taking place in the United Synagogue and other central Orthodox communities have fallen from nearly two thirds to just under half. Meanwhile, Charedi marriages have risen from one in ten to nearly three in ten at the latest count.
Since 2005, there have been more Jewish births recorded each year than Jewish funerals: 3,313 births in 2007 (the last year for which a figure has been calculated) compared with 2,734 deaths in 2010.
However, Daniel Vulkan, author of the Board's new demographic report, cautions against assuming that British Jewry, after years of numerical decline, has begun to grow again. "There is no accurate means of assessing migration to or from the UK," he writes. "And, while data may be available on the number of people choosing to convert to Judaism, it is not possible to say how many people decide each year that they no longer wish to identify as part of the Jewish community."
The Board says its figures are "conservative estimates" because they exclude non-religious circumcisions performed on Jewish babies by doctors as well as some carried out by strictly Orthodox mohelim who are not members of the Initiation Society (which regulates traditional practitioners).
The extent of the rise in Charedi births, however, can be gleaned from announcements for a shalom zachor, a celebration for the birth of a boy. In Manchester and Stamford Hill alone, the number of Charedi boys born leapt from 546 in 2007 to 710 in 2010. Although the figure fell to 663 last year, it is "too early" to say whether this indicates that Charedi birth rate is slowing down, the Board says.
While Jewish marriage rates appeared "flat" for the decade up to 2007, the latest statistics instead show "a gradual decline" in recent years.
The Board does not collect data on secular marriages between Jews, same-sex ceremonies or blessings for mixed-faith unions given in synagogue.
Non-Orthodox marriages fell slightly in quarter of a century from nearly 25 per cent in the 1981-5 period to under 23 per cent in 2006-10.
Also down was the number of Jewish religious divorces, which decreased in two decades from 277 in 1992 to 221 in 2010.
Our community by the numbers:
Jewish religious marriages in 2010, lowest total ever since records began
Jewish births recorded in 2007
Year records began being kept by Board of Deputies
of all Jewish births are Charedi children
Jewish deaths recorded in 2010
Charedi boys born in 2010 in Manchester and Stamford Hill
2 in five
Jewish babies born in the UK are born to strictly Orthodox parents
3 in 10
Jewish marriages are Charedi