Cameron facing Commons defeat over gay marriage plans However, Downing Street sources warned yesterday that the Prime Minister would not support extending civil partnerships beyond their current application because he believed marriage was the best way to recognise commitment in relationships. Other government sources suggested that extending civil partnerships would hit the Treasury with an extra £4 billion in pension liabilities. Senior Tories have urged their colleagues to support the law when the Marriage (Same Sex Couples) Bill returns to the Commons today for the report stage and third reading. Francis Maude, the Cabinet Office minister, describes in The Daily Telegraph today how the death of his gay brother from Aids convinced him to support moves to legalise marriage for same-sex couples. He says his views were shaped by the death of his brother Charles in 1993, when "society was a far less accepting place for gay men such as him." However, Mr Maude's view is fiercely opposed by many of his Conservative colleagues who take a traditionalist and often Christian view of marriage. It is understood that Owen Paterson, the Environment Secretary, is strongly likely to vote for amendments tabled by the Tory MP David Burrowes, intended to prevent the "erosion of traditional marriage." MPs and ministers are being given a free vote and will not be required to follow party instructions because it is seen as an issue of conscience. Mr Loughton's amendment to the Bill extending civil partnerships to heterosexuals for the first time is believed to be gathering considerable support. Some believe that if his amendment is passed, ministers may be forced to abandon the Bill entirely. Helen Grant, the justice and equalities minister, said such a radical change must not be introduced in a "rush." She added that civil partnerships should be reviewed once gay marriages had been operating for five years. An informal group of church leaders, warn today that hundreds of thousands of Christian young people will be put off becoming teachers, doctors, nurses or other public servants once gay marriage becomes law. In a letter to The Daily Telegraph, they call on MPs to make urgent amendments to the Bill to protect Christians and others with traditional views from being punished in the workplace for their beliefs.