BySimon Rocker, Simon Rocker
The Reform and Liberal movements have agreed a formal alliance, pledging greater co-operation in order to strengthen the overall Progressive presence within the community.
Although merger talks took place between the two movements 30 years ago, they have never been reopened.
Now, leaders believe closer ties will give them more scope to reach out to the growing pool of secular and unaffiliated Jews. Liberal Judaism chairman Lucian Hudson has long advocated closer collaboration.
His Movement for Reform Judaism counterpart, Robert Weiner, said: "Lucian and I have had several conversations in recent months. We are acutely aware there is a shift in the Jewish population as proven by the JPR report.
"It is important that unaffiliated Jews know that there is a meaningful option in Judaism that will appeal to them - that is the key driver."
The more we co-operate, the stronger our voice
The alliance would enable them to speak with a single Progressive voice "where it makes sense, as opposed to a Reform or Liberal voice".
Over the past few decades, the number of self-identifying Progressive Jews has risen from 15 per cent to 18 per cent of the community, according to the Institute for Jewish Policy Research (JPR). Secular or cultural Jews make up nearly a quarter of the Anglo-Jewish population.
"Everyone we have spoken to is up for the idea," Mr Hudson reported. "We are responding to a mood for working more closely together."
The two movements are particularly looking to collaborate on student chaplaincy and social action, adding to their joint efforts in areas such as rabbinic training. Both movements are members of the World Union for Progressive Judaism.
Practical details of the alliance will be worked out by a group of rabbinic and lay leaders. "There hasn't always been the framework to do that," Mr Weiner said. "We have taken the obstacles away."
He insisted that the move "has not been driven by finances at all".
Individual synagogues would continue to remain members of their umbrella movements. "There are still differences between the Liberal Jewish Synagogue and West London Synagogue, or Finchley Progressive and Finchley Reform."
Liberal chief executive Rabbi Danny Rich observed that "the biggest dividing line in British Jewry is no longer Orthodox and Progressive, but religiously engaged or secular.
"We believe that, together, the two movements can provide an outward-looking, modern and relevant alternative to a merely secular form of Judaism."
Reform's senior rabbi, Laura Janner-Klausner, commented: "The more we can co-operate, the stronger our voice, and the stronger the expression of the core values we share - inclusiveness, integrity and informed choice.
"These are the values our movements believe will enable Judaism to survive and thrive in the 21st century."