The Movement for Reform Judaism has officially backed gay marriages in a week in which church leaders have renewed their opposition to marriage equality for gays.

The Reform Movement said such a move “can only strengthen society and the institution of marriage”.

The Movement joined Liberal Judaism, Unitarians and Quakers in officially supporting equal marriage rights for gay couples.

It has conducted gay commitment ceremonies since February 2011, recognising a greater diversity of relationships within its communities in what it called a “general move to greater inclusivity”.

Representing 42 synagogues with a membership of approximately 30,000, together with Liberal Judaism the groups represent about a third of British Jewry.

Rabbi Colin Eimer, who chaired the Assembly of Reform Rabbis UK working party said: “We are focused on what constitutes good Jewish relationships, be they heterosexual or homosexual.

“Religious ceremonies exist in Jewish life for heterosexual couples to express their love, commitment, values and ideals. We believe that homosexual couples should have that same opportunity for a religious ceremony within the sanctity of Jewish community, tradition and practice.”

Reform Movement Rabbi, Rabbi Laura Janner-Klausner says: “A recognition of equality of marriage for homosexuals as well as heterosexuals can only strengthen society and the institution of marriage.

“We welcome moves to legislate to this end. We are all made in God’s image, an image that has a wide prism of characteristics and believe therefore that same-sex partnerships based on the same stability, faithfulness, love and mutual support as heterosexual relationships should be seen as fully equal in the eyes of the law.”

Rabbi Aaron Goldstein, co-chair of Liberal Judaism’s Rabbinic Conference, said: “I’m delighted that the Movement for Reform Judaism have now publicly come round to our view and decided to join Liberal Judaism, the Quakers and the Unitarians in pushing for full marriage equality. We look forward to welcoming them into a group of progressive religions that will try to help the Government to form policy that reflects the reality of the vast majority of our society. In 2005 Liberal Judaism became the first ever religious movement to publish official liturgy for same-sex commitment ceremonies and we have proudly performed countless ceremonies since that time. It has always been our long term aim to do everything within our power to make marriage equal for all people, both gay and straight.”

The announcement follows a damning indictment of gay marriage by Cardinal O’Brien, head of the Scottish Catholic Church, who called the proposition of equal marriage “grotesque” and likened it to the reintroduction of slavery.

The Archbishop of Westminster, head of the Catholic Church in England and Wales has distributed a letter which will tell Catholics who attend Mass this weekend of their “duty” to oppose gay marriage rights.

Meanwhile, the Times reports that former Bishop of Oxford Lord Harries of Pentregarth has said the Church of England is “to blame” for the current squall over marriage.

Lord Harries said: “The Churches have only themselves to blame for their current predicament, in which they face a major rewriting of the law on marriage.

“Instead of at first opposing civil partnerships, and then only accepting them grudgingly with gritted teeth, they should have welcomed them warmly from the first and immediately proposed services of commitment and blessing in church. They should do this even now.”