British Masorti has followed the Liberals and Reform movements by taking a historic decision to allow its rabbis to conduct same-sex marriages.
Gay couples will now be able to marry in Masorti synagogues in a move approved without opposition by the movement's trustees on Tuesday night.
Rabbi Jonathan Wittenberg, senior rabbi of Masorti Judaism and head of its largest synagogue, the New North London, said, "This is an important step forward. As a movement, we will continue to strive to be inclusive and to honour the dignity of all people, within the framework of Jewish law."
Same-sex couples will be able to have a shutafut - partnership - ceremony, which technically distinguishes it from kiddushin, the traditional Jewish marriage ritual. But the ceremony will enable them to register as either married or as civil partners under English law.
Each of Masorti's 12 communities will be free to decide whether to hold the new ceremonies, although no community has objected to the innovation.
It shows tradition can be combined with modern values
Joel Fenster, director of Masorti's youth movement, Noam, hailed a "landmark decision".
Masorti Judaism chief executive Matt Plen said he was proud to be part of a movement "which demonstrates by its actions that traditional religious commitment can be combined with deeply-held modern values".
But the decision, which will put further distance between Masorti and Orthodoxy, has also drawn criticism.
Ivor Jacobs, son of Masorti founder Rabbi Dr Louis Jacobs and a New North London congregant, said: "Gay people have never been discriminated in the shul but these ceremonies are a move too far. This is a watershed for Masorti, which may well impede any possibility of further discussion with modern Orthodox over issues of Jewish status."
Former Masorti executive director Dr Harry Freedman said that there was no doubt that Rabbi Jacobs would have "been forcefully opposed even to the concept of single-sex marriage, let alone its validation in synagogues. Masorti has drifted far from his views on many issues, but this latest decision probably marks an irrevocable renunciation of their founding purpose."
Same-sex marriages were first legalised in Britain in March, although same-sex couples had for several years been able to have their union blessed in Reform or Liberal synagogues.
Masorti, which has always eschewed the "Progressive" label, is allied to the Conservative and Masorti movements in the United States and elsewhere. The American Conservatives have conducted same-sex marriages since 2012, while some Israeli Masorti rabbis also perform them, although they do not have the status of marriage in Israeli law.
The name shutafut was chosen to show that the ceremony is an innovation in Judaism rather than part of the normal halachic tradition.
This week's decision, which follows consultations with Masorti communities begun earlier this year, is based on rulings from Conservative religious authorities in America.
They regard the principle of kavod habriot, human dignity, as overriding longstanding Jewish prohibitions against homosexual unions.
Benjamin Ellis, director of Keshet UK, which supports lesbian, gay, bisexual and transgender Jews, said the move was "fantastic news. It means LGBT people can stay in their communities with the partner they love, without feeling that their relationship doesn't count."
But Rabbi Baruch Davis, chairman of the Rabbinical Council of the United Synagogue, said, "The Torah is pretty clear in its opposition to homosexual relationships. We can be understanding of people in their relationships but we who believe in the God-given Torah can never sanction something the Torah can't."
