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LONDON — The Jewish community of England, with its proud history as the one-time champion and spokesman of world Jewry, is today declining in number and influence, while mirroring some the maladies of its American brethren.

According to a recent survey on British Jewry, 50 percent of Jewish men under 30 have non-Jewish spouses or partners; about half of all Jews consider themselves "secular" or "just Jewish"; and support for Israel is waning as concerns for domestic needs rise.

The malaise of British Jewry goes back to the beginning of the century, but the real sea change in the attitudes and fortunes of the community dates from the end of World War II to the present, said Professor Geoffrey Alderman.

"Roughly, we have a situation in which the religious extremes are gaining at the expense of the center, while at the same time the whole is contracting," the Oxford-educated academic said.

Alderman, who is Orthodox, is the foremost historian of contemporary Anglo-Jewry.

The "shrinking whole" is reflected in the numbers. There are about 300,000 "self-identifying" British Jews, Alderman noted, down from more than 400,000 in the 1960s.

"We are now shrinking at the rate of 1 percent per year, due to emigration, mainly to Israel, assimilation, and, foremost, contraception," Alderman said.