Around half of Jewish babies born in Britain will be strictly Orthodox within a generation, according to a report issued by the Institute for Jewish Policy Research this week.
Charedim currently represent just under one in six of British Jewry, but owing to the community's high birth rate, their children comprise 30 per cent of all Jewish children in Britain.
If high Charedi birth rates continue, 50 per cent of Jewish children and around 30 per cent of young adults in the UK will be strictly Orthodox by 2031, the report says.
"Strictly Orthodox Jews are expected to constitute a majority of the British Jewish population long before the 21st century is over," say authors Daniel Staetsky and Jonathan Boyd.
Analysing data from the 2011 Census as well as community surveys, they say that the strictly Orthodox community is increasing at a rate of 4.8 per cent a year, while the non-Charedi Jewish population is declining by 0.3 per cent.
Their high birth rate - at seven children per mother - is more than three times that of the overall Jewish figure of 1.98 in England and Wales and the national population at 1.93. The birth rate is 3.25 for English and Welsh Muslims and 1.53 for Christians.
Among Charedim, there are 137 young people under the age of 20 for every 100 between the ages of 20 to 64 - a child dependency rate higher than for countries in Africa and the Middle East.
By contrast, the rate is 37 for every 100 among Jews in England and Wales overall and 40 per 100 for the UK population as a whole.
But the report, Strictly Orthodox Rising, warns of challenges ahead, noting that social scientists have generally linked a high proportion of young people in a population "to social and political unrest and growth in criminality, especially in the absence of attractive employment prospects".
However, the Orthodox charity Interlink Foundation, said the report was flawed and significantly understated the size of the Charedi community.
JPR gives the strictly Orthodox population currently as a maximum of 43,571, but Interlink argues that the true figure is 58,500. The point at which Charedi births represent 50 per cent will be reached much sooner than 2031, the charity said.
Interlink also criticised the "reprehensible" comments on potential unrest among youth. "Whatever economic issues face the Charedi community - and in other parts of the world they are much more severe than in the UK - they have never remotely been linked to social and political unrest and criminality," it said.
The charity also expressed concern about the tone of the report, claiming that even the title was suggestive of a threat posed by the community.
Interlink rejected "completely the relevance or usefulness of the commentary about the Charedi 'youth bulge'.
"We are concerned about possible malicious uses of these aspects of the report."
