The number of American Jews is growing, not declining, according to a new study from Brandeis University.

Leonard Saxe, a professor at Brandeis's Steinhardt Social Research Institute, found that the number of Americans who identify themselves as Jewish has risen from 5.5 million in 1990 to 6.5 million.

Mr Saxe made his estimate by analysing data from 150 surveys taken by the US government and polling organizations. It challenges the finding made in a 2000-2001 National Jewish Population Survey conducted by the Jewish Federations of North America, which estimated that the US Jewish population had declined by 300,000 over a decade.

The new research project which Saxe unveiled last week in Boston also examined a sample of 1,400 Jews surveyed by Knowledge Networks, a polling firm, and found that 80 per cent identify as Jews on the basis of religion, while the remaining 20 per cent choose another criterion to define themselves as Jewish.

Those who identify on the basis of religion were far more likely to marry a Jewish partner and to participate in Jewish events like barmitzvahs, Jewish weddings and shivahs, the survey found.