The Lawyers' Christian Fellowship (LCF) and Evangelical Alliance will be praying for a miracle when they join other Christians in prayer outside Parliament tonight as peers take the final vote on the controversial gay rights bill.

"We pray for a miracle," the LCF said. "However, whatever the outcome, it is vital that history records Christians standing for truth to the very end of the parliamentary process."

Hundreds of Christians are expected to turn out for the prayer vigil outside Parliament tonight , organised by Christian Concern for Our Nation. As Christians pray, MPs inside will take the final vote on the draft Equality Act Regulations 2007 (SORs), approved by the House of Commons on Monday night by 310 to 100 votes.

Andrea Minichiello Williams, Public Policy Officer for the LCF, criticised the churches for not speaking out enough in protest to the regulations.

"The church needs to point people to how to live, not reflect society," she told Christian Today. "For too long we have allowed society's values almost to mould us and we need to stand up for biblical truth because that truth is good not just for Christians but for the whole of society."

If the regulations do go ahead, she said she hoped that "as the implications of the SORs unravel the church will then awaken to the imposition of secularism and stand up for truth; that they will choose to obey God rather than man".

The Evangelical Alliance said Christians should join in prayer, adding that the decision made could have a historic impact on the legal landscape for British religious liberties.

Dr R David Muir, the Evangelical Alliance's Director of Public Policy, said: "We want to encourage Christians to pray, because this could be a significant moment for religious freedom for Christians and other people of faith."

The LCF is among a number of Christians who have accused the Government of rushing through the regulations in order to stifle proper debate.

In a letter to The Times, the Ven Norman Russell, Prolocutor of the Convocation of Canterbury and Archdeacon of Berkshire, and the Rev Canon Glyn Webster, Prolocutor of the Convocation of York and Canon Chancellor of York Minster, criticised the lack of democratic debate on the regulations.

"The House of Lords has an opportunity on Wednesday to address the democratic deficit and insist that these matters of policy are put in a bill by rejecting regulations which they can neither amend nor debate fully," they said.

The head of the Catholic Church in England and Wales, Cardinal Cormac Murphy-O'Connor, meanwhile, criticised Monday night's last-minute meeting to pass the final draft of the regulations.

"It is, surely, an abuse of parliamentary democracy that these regulations are being considered by Parliament only through a hurriedly arranged and very brief meeting of 16 appointed MPs, and a short debate in the House of Lords," he said.