A number of senior Orthodox rabbis have hit out at Prime Minister David Cameron's support for the legalisation of gay marriage.

But Lord Sacks, who would have the opportunity to vote on the issue if it were to reach Parliament, would not comment on it.

Mr Cameron made a point of mentioning his backing for the move in his speech to the Conservative Party conference earlier this month, repeating his opinion before he became PM that "it shouldn't matter whether commitment is between a man and a woman, a woman and a woman, or a man and another man".

But his words were met with dismay by Dayan Yisroel Lichtenstein, head of the Federation Beth Din, who said that gay partnerships ran "counter to Torah values".

He said: "Promoting legalisation of gay marriages is to sanction them and is a sign of moral decay in the legislature of a society. I am profoundly disappointed in Mr Cameron who… is prepared to sacrifice moral values for popularity."

Rabbi Yitzchak Schochet of Mill Hill United Synagogue said that while discrimination against minorities was always wrong, "however, regardless of individual life-choices, the time-hallowed sacredness of marriage should always be preserved.

"Progress is not determined by blurring the lines between traditional values and modern-day political correctness.

"Inasmuch as government feels it needs to accommodate modern trends, this should not be at the expense of certain inviolable institutions that have been upheld for the past millennia and always served as the foundation of our society."

Rabbi Alan Plancey, a Conservative local councillor in Hertfordshire, said: "It is a shame that the standards of morality seem to be dropping all the time and we seem to be legalising everything and anything."

But Rabbi Mark Goldsmith, chairman of the Assembly of Reform Rabbis UK, welcomed the government's initiative. "For some years now Reform rabbis have been helping lesbian and gay Jewish couples to celebrate and confirm their lifelong commitment through Jewish ritual. This is currently the religious counterpart to the civil partnership ceremony. It would be a delight for our Jewish commitment ceremony to be the religious counterpart to a civil marriage."

The government introduced commitment ceremonies for gay couples to publicly affirm their union six years ago but these do not have the force of marriage and currently cannot be held under religious auspices.

Blessings for same-sex couples in Progressive synagogues have to take place separately from a secular commitment ceremony.