The head of the United Synagogue’s Rabbinical Council (RCUS) has responded to a call for a common conversion standard by asserting that only Orthodox conversions are valid.

Jonathan Arkush, the Board of Deputies’ senior vice-president and a US member, publicly revived the idea of a unified approach at a Board meeting last week in order to prevent disputes over who is a Jew.

But RCUS leader Rabbi Yitzchak Schochet said this week: “Reform and Liberal and conversions are generally not accepted by Orthodox and Masorti movements. Masorti conversions cannot be accepted by Orthodox. The only one that is acceptable throughout is Orthodox conversion.”

He said that both converts and the rabbis converting them were required to accept the truth and demands of the Torah and Jewish law. “This, of itself, excludes the possibility of a rabbinic court that has members that do not qualify as such,” he declared.

Rabbi Tony Bayfield, head of the Reform movement, welcomed Mr Arkush’s call but added that progress would depend on a change of heart within the Orthodox authorities.

“If the mood of the community has changed sufficiently for it to prompt the London Beth Din to change its position, that would be great,” he said. “I think that the mood is changing but I don’t see any evidence of the Beth Din being prepared to move from its position, which denies all rabbinic authority to the non-Orthodox movements.”

He continued: “Would they really be prepared to rubber-stamp conversions performed by others even if those conversions were in conformity with tradition — eg milah (circumcision), tevillah (immersion in a mikveh), study, mitzvot? It still leaves open the question of whether Reform and Liberal would accept such a rubber- stamping.”

A spokesman for the Office of the Chief Rabbi commented: “There are fundamental differences between Orthodox and non-Orthodox approaches to conversion, and these need to be recognised.  It is important to pursue any approach that can bridge divisions within our community, while acknowledging diversity.”

Rabbi Jonathan Wittenberg, senior rabbi of the Masorti movement, said a common conversion policy would be “halachically and politically challenging, but that doesn’t mean it isn’t worth investigating.

“Our community should try to do its utmost to avoid hurting individuals, and this is an issue where people get hurt.”

Rabbi Bayfield said the problem lay in the London Beth Din’s insistence that converts pledge themselves to a strictly Orthodox lifestyle rather than accept a broader commitment to lead Jewish lives.

But Rabbi Schochet said that relaxing the conversion requirements would be like someone deciding “he wants to be recognised as a British citizen on his terms… and then setting up his own naturalisation court. Surely this is altogether absurd and unacceptable, as it is no more than total anarchy that destroys the concept of normative citizenship.”

The last bid to institute a common policy was 20 years ago when the then Liberal leader Rabbi Sidney Brichto put a proposal to the Chief Rabbi Lord Jakobovits.

The Progressives would stop doing conversions themselves but instead send prospective converts to the London Beth Din in return for a “lenient” approach. The Beth Din could “demand only knowledge of Orthodox practice and not its observance”, Rabbi Brichto suggested.

Lord Jakobovits rejected the compromise, although Sir Jonathan Sacks told Rabbi Brichto at the time that his initiative represented “a way forward”.