Members of Borehamwood and Elstree Synagogue will have to wait a little longer for their rabbi to elaborate on why he is leaving after four years.

In a letter to congregants last month, Rabbi Naftali Brawer had promised to speak about his decision to join a new national foundation promoting spirituality in the workplace during his sermon last Shabbat.

But the packed congregation which had turned up to hear him was forced to be patient as he was unwell.

Rabbi Brawer, 41, said this week that he would give what he planned as "a fireside chat" to the community at a later date.

But he stressed that his departure at the end of August was "not about quitting Borehamwood and Elstree. It's about a rabbi being given an extraordinary opportunity that most people don't get. I am passionate about it."

It is unusual for a rabbi of his seniority to move out of the pulpit. But United Synagogue communities in the growing Jewish population of Hertfordshire are finding it hard to hang on to their rabbis for long. Rabbi Ariel Abel, who left Radlett after nearly five years last summer, has taken a break from congregational work. Rabbi Natan Levy of the newest community, Shenley, is making aliyah in summer after three years.

By contrast, Rabbi Brawer's predecessor, Rabbi Alan Plancey, served Borehamwood for 31 years until his retirement in 2007.

Borehamwood member Jonathan Arkush said Rabbi Brawer's departure would be "a great loss" to the congregation."He has been an inspirational rabbi who has taken our community on a spiritual journey. His sermons and educational initiatives have attracted a large following."

But another congregant was sceptical about members' appetite for education, suggesting that although Rabbi Brawer was an "exceptional speaker and academic", his successor would need to be more focused on pastoral work.

"In Rabbi Plancey, we had one of the archetypal pastoral rabbis and they don't make rabbis like that anymore."

A supporter of Rabbi Brawer said the minister had endured some "sniping in the background" from elements in the 1,300-family congregation. The rabbi was "one of the stars" of the community whose new enterprise would provide "a great national canvas for his talents".