Diaspora Jews are under increasing threat from assimilation due to a lack of “mission causes”, according to an international expert on Jewish history.

Brandeis University’s Professor Jonathan Sarna made the statement while delivering the first William Frankel memorial lecture last week, in memory of the former JC editor and chairman, who died last April.

Professor Sarna told the 100-strong Institute for Jewish Policy Research audience that the recession would reduce communal expenditure, “which would weaken links to Jewish identity for a generation of youngsters”.

On the issue of antisemitism, he felt that the recent examples of “affinity frauds”, including the “Madoff affair and many mini-Madoffs”, were outside the “antisemitic stereotype of Jews stealing from non-Jews”.

He added: “Antisemites who blamed Jews for the economic crisis knew Jews were responsible before it happened.”

Professor Sarna was pessimistic about assimilation. Because of the concentration of Jews in Israel and the US, and the rescue of Jews from the former Soviet Union and developing world, he believed that diaspora Jews had “exhausted many of their well-defined missions”.