Religious leaders issued a fresh appeal to David Cameron to halt plans to allow gay marriage, suggesting it would "devalue the meaning" of the institution.
A letter to the Daily Telegraph, signed by 61 people describing themselves as "leaders of Britain's major faiths", said the controversial legislation was being rushed through Parliament without proper debate.
Christian, Jewish, Muslim, Hindu and Buddhist figures were among those behind the appeal for a "pause".
The Marriage (Same Sex Couples) Bill arrives in the Lords on Monday for the start of what is expected to be a stormy passage through the upper chamber.
It survived a Commons backlash when 130 Tory backbenchers opposed the move.
Bishop Michael Hill, the Anglican Bishop of Bristol, Archbishop Bernard Longley, the Roman Catholic Archbishop of Birmingham and Bishop Angaelos of Britain's Coptic Orthodox Church, were among signatories.
Others included Sir Iqbal Sacranie, a former head of the Muslim Council of Britain, Rabbi Natan Levy, an adviser to the Board of Deputies of British Jews, Bhai Sahib Bhai Mohinder Singh, a Sikh community leader and John Beard, a prominent Buddhist.
"The haste with which this legislation is being driven through Parliament and the failure to talk to all religions will mean that the problems which we have repeatedly highlighted will be written into law with serious and harmful consequences for the health of society, family life, and human rights such as freedom of religion and of speech," they wrote.
Dismissing safeguards in the proposed law as insufficient, they wrote: "It is surely clear that there are significant problems with this legislation which require further scrutiny and probably amendment.
"We therefore urge you to pause so that this may take place."
"Because of its serious flaws we will continue to resist this proposed legislation and to highlight its injustice and unfairness. It creates a two-tier form of marriage in one of which the importance of consummation, procreation and the welfare of children, as well as issues such as adultery have been ignored, and devalues the meaning of marriage itself."