Religious leaders have written an open letter to the House of Lords calling on them to reject the challenge facing the regulations for religious civil partnerships tomorrow.

Representatives of Quakers in Britain, Unitarians and Liberal Judaism are urging the upper house to dismiss Baroness O’Cathain’s attempt to repeal the new rules, which came into force on 5 December.

The argument to be used is that the regulations do not offer sufficient protection to religious bodies who do not want to hold civil partnership ceremonies, but do want to hold weddings. It suggests they may be forced, under equality rules, to perform both or neither.

The Church of England rejected that argument, and specific provisions were included in the law to avoid such a situation.

The open letter, sent to the three main parties in the House of Lords, says the new laws are clear on the issue and will allow organisations to “say no as well as yes”.

Today’s letter reads: “Liberal Judaism, Quakers in Britain and the Unitarians and Free Christians have indicated that they would wish to take up the opportunities offered by the legislation which was passed with support from all parties.

“We recognise fully the rights of those who did not wish to do so and are clear that the legislation protects the freedom to say no as well as yes.

“We do not believe the state should force churches or faith communities to act against their sincerely held beliefs; however, we claim the same right in accord with our own deeply held views of equality and justice.

“Our wish to undertake civil partnerships registration in a religious context reflects our shared commitment to the inherent worth of each individual and our respect for loving relationships between people of the same sex.

“There has been growing acceptance in England and Wales of a broader view of what family means reflecting the increasingly varied pattern of relationships, including same sex couples.

“Faith communities like our own have similarly embraced this diversity. We were pleased that Parliament recognised this when it approved civil partnership registration in religious premises. We look forward to putting in place this legislation.”

The letter was signed by Paul Parker, Recording Clerk for Quakers in Britain, Derek McAuley, Chief Officer for General Assembly of Unitarian and Free Christian Churches and Rabbi Danny Rich, Chief Executive of Liberal Judaism.