A new report has sparked fresh debate on the size of Britain’s rapidly growing strictly Orthodox population.

The UK Charedi population numbers between 22,800 and 36,400 and has been growing at a rate of four per cent annually since the early 1990s, according to a study published this week by the Board of Deputies’ community policy research group.

But Charedi sources maintain that even the higher figure is an underestimate and that the total is above 40,000.

David Graham, joint author with Daniel Vulkan of the 20-page report, stressed: “It is not by any means the last word on the subject. If anything, it is the beginning of the debate.”

The Charedi are thought to comprise around 10 per cent of Britain’s 300,000 Jews, but if they continue to grow at the present rate, while the overall Jewish population continues to decrease, they are likely to form a majority of UK Jewry within a generation or so.

Booming: members of the Charedi community shop in North London

“In a Western, diaspora Jewish population, to be growing at four per cent is astonishing,” Mr Graham said. “If we had that for the Jewish population generally, we’d be over the moon.”

A third of all Jewish children in the UK under 18 are now strictly Orthodox, according to the report, and there are 1,400 to 1,500 Charedi babies born each year.

The report is based on a number of sources, including the 2001 Census records; shalom zachor celebrations for baby boys announced in local news-sheets; Orthodox directories for Sabbath-observant families; and enrolment at Charedi schools.

The largest concentration of Charedi Jews — in Stamford Hill, North London — is estimated to range from 10,792 to 18,727; in Broughton Park, North Manchester, from 6,433 to 9,300; in Golders Green, Hendon and Edgware, North-West London, from 4,012 to 6,679; and in Gateshead, around 1,564.

But Rabbi Avraham Pinter, a strictly Orthodox member of the London Jewish Forum, believes that a more realistic figure is 41,000 overall. He argues that the Board has significantly underestimated the North-West London Charedi population and that the Stamford Hill community is also bigger.

A recent survey prepared for Hackney Council estimates the Stamford Hill strictly Orthodox community to be 19,700.

“The haemorrhaging of the Jewish community has stopped,” Rabbi Pinter said. “We are starting to look at growth and we should plan accordingly. The modern Orthodox are also growing, for anyone willing to open their eyes.”

According to the Board estimates, 735 strictly Orthodox babies were born in Stamford Hill last year, 321 in Broughton Park and 250-350 elsewhere.

The Manchester community appears to have experienced the fastest growth at 5.5 per cent, compared with 3.3 per cent for Stamford Hill.

Strictly Orthodox marriages have increased at an annual rate of four per cent since 1990, comprising more than a quarter of all Jewish marriages by the middle of the decade.

The report also reveals that 69 per cent of strictly Orthodox engagements announced in Stamford Hill in 2007 involved one non-British partner.

It also notes the “dramatic fall-off” of boys leaving Jewish day schools in Stamford Hill after the age of 12.

“This is due to boys leaving these schools around the age of barmitzvah in order to attend yeshivot,” it says.

In 2007, there were 213 boys and 239 girls in Year 7 — the first year of secondary schools — in Stamford Hill schools; 119 boys and 226 girls in the next year; just 20 boys and 198 girls in year nine; and in the GCSE year, 197 girls and a single boy.