A Conservative peer will tonight lead an eleventh-hour attempt to defeat proposals that the Roman Catholic Church says could lead to the closure of its adoption agencies.

The Equality Act (Sexual Orientation) Regulations, which outlaw discrimination against gay people in the provision of goods and services, was the subject of fierce debate about its impact on adoption agencies. But Baroness O’Cathain will highlight separate anxieties over its effect on church schools.

Her motion raises concerns that the regulations compromise religious liberty and “will result in litigation over the content of classroom teaching”, and says they should be rejected.

The debate will draw attention to splits in Conservative ranks over social policy and raise questions over the commitment of the party to David Cameron’s approach. Tory peers have a free vote, but Labour and Lib Dem peers have been told to support the regulations, so they should be passed. On Monday night MPs approved them by a big margin, without debate, but Mr Cameron was among just 29 Tories who voted in favour; 85 voted against. Analysis by Professor Philip Cowley of Nottingham University showed that only six of the Tory MPs who entered the Commons at the last election supported the regulations, demonstrating that opposition is not confined to older MPs.

Some of the Conservative MPs who voted against the new laws were protesting at what they saw as insufficient parliamentary debate; others opposed them on principle.

Earlier this year a group in the Cabinet led by Alan Johnson, the Education Secretary, pressed for the swift application of the regulations, while Ruth Kelly, a Catholic who as Communities Secretary has responsibility for equality policy, argued that Catholic adoption agencies should be exempted.

The Prime Minister imposed a compromise under which the Church’s adoption agencies were given a transitional period of 20 months to prepare for the legal change, but not the exemption sought by its bishops.

Under the regulations, gay people would be able to sue if they believed that they had been refused services – whether by an adoption agency or other entities such as a hotel – because of their sexuality.

Last night Christian groups accused the Government of “trying to bury bad news” by scheduling the final vote on Budget Day. Hundreds of Christian protesters are planning a mock funeral procession in Parliament Square, to demonstrate against the “death of morality and democracy”.

The Roman Catholic Archbishop of Westminster, Cardinal Cormac Murphy-O’Connor, accused Tony Blair of an “abuse of parliamentary democracy” in forcing the regulations through the Commons on Monday night with no debate and a single vote which the Government won. “Profound public concern about aspects of these regulations has not been heard,” he said.

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