Seven rabbis have quit the Reconstructionist movement in the United States and more are considering leaving after the organisation announced that it would let its rabbis marry non-Jewish partners.

The progressive denomination, loosely affiliated to the Conservative movement, counts more than 100 congregations, but the September policy change has prompted a wave of exits, with some saying the new ruling is “detrimental to America’s Jews”.

Rabbi Reba Carmel, who serves a non-denominational synagogue in Pennsylvania, said she was concerned that “ultimately we will be assimilated out of existence”. She added: “It goes to the heart of what it means to be a Jewish leader.”

The Reconstructionist Rabbinical Association was unapologetic, saying that while seven rabbis had left, four rabbis ordained by other non-Reconstructionist seminaries have taken steps to join the movement since the policy was announced.