Chief Rabbi Ephraim Mirvis has warned United Synagogue rabbis to avoid inviting “inappropriate” speakers in a confidential memo sent to them and the chairmen of their synagogues a few days ago.

He wrote that it had been prompted by a number of recent developments in communities which had cause him “great concern”.

He said that he had previously made rabbis aware of the importance of not offering a platform “to speakers who are inappropriate” at his rabbinical conference in July.

Synagogues should not host speakers who represent an outlook “which encourages practices which run contrary to our normative United Synagogue approach”.

The memo gives no detail about the incidents that have caused concern or about potentially undesirable speakers.

But rabbis who wanted further information were invited to discuss with him the position he and the London Beth Din had taken, in the hope of avoiding “further situations where any options for action are considered after the fact”.

One source familiar with the contents of the memo described it as “vague and indistinct – no one has a clear idea of what he is talking about”.

But he speculated that it might partly be in response to the recently announced appointment of Dina Brawer as scholar in residence at Hampstead Synagogue.

Mrs Brawer, the UK ambassador for the Jewish Orthodox Feminist Alliance, is the first student from Britain to enrol at New York’s Yeshivat Maharat, an institution which ordains Orthodox women as spiritual leaders.

A spokesman for Rabbi Mirvis would only comment, "The Chief Rabbi frequently advises Rabbis on a wide range of educational, halachic and practical matters.”