“Discussion about changing same-sex marriage laws has been a topic of discussion across the world-wide Anglican communion, and resolutions at the Australian General Synod consistently support marriage between a man and a woman in lifelong union, based on Scripture,” Dr Aspinall said in a statement. But Dr Catt says the proposed Marriage Equality Amendment Bill addresses what philosopher John Rawls called a foundational principle of justice, “that each person is to have an equal right to the most extensive total system of equal basic liberties compatible with a similar system of liberty for all”. Dr Catt says the current Marriage Act denies legal and social recognition to same-sex couples, recognition that is “available to all opposite-sex couples with legal capacity, regardless of any other characteristic”. “Recognising the union of same-sex couples doesn't reduce the liberty of other couples to enter into legally- and socially-recognised partnerships – so there is an inherent injustice in preventing same-sex couples from doing so,” he says. Dr Catt notes churches will not be forced to marry same-sex couples, saying the Marriage Act will continue to enable the conduct of both civil ceremonies and those conducted by ministers of religion.

“I therefore commend the fact that the proposed legislation will not affect the right of churches or other religious groups to celebrate marriage according to their own understanding and religious beliefs,” he writes. “I believe the inclusion of this provision will provide a position space in which religious groups will be able to have their own internal debates and conversations about their approach to marriage. “This in turn allows for these sectarian debates to be separated from the debate as it applies to the nation as a whole. I see this as honouring the pluralistic nature of Australian society.” Dr Catt's letter is one of many submissions lodged by religious leaders as a Senate inquiry considers a bill to allow same-sex couples equal marriage rights to heterosexual couples. Six Victorian Catholic bishops last week wrote to their parishioners urging them to oppose same-sex marriage, arguing Australian society would “flourish only if the true meaning of marriage is preserved for future generations”.

“A grave mistake will be made if such legislation is enacted,” the six Catholic leaders wrote. “The Government cannot redefine the natural institution of marriage, a union between a man and a woman. The Government can regulate marriage, but this natural institution existed long before there were any governments. It cannot be changed at will.” The Presbyterian Church of Queensland's submission to the inquiry argues the Marriage Act should not be further amended to allow same-sex marriage “because homosexual practice is a sinful act in the sight of God, and because the status of marriage will be eroded”. But prominent Brisbane-based advocate Shelley Argent, of Parents and Friends of Lesbians and Gays in Australia, says same-sex marriage is working overseas without any detrimental effects to the churches or society generally. In her submission, Mrs Argent says her gay son, who worked for the Queensland Police Service, felt he had to do more to prove himself than others and should have the right to marry the person he loved.

“When James was in the police force, he was good enough to go into dangerous situations, where many straight men wouldn't dare, he was good enough to be in charge of the watch house and keep guard over murderers, rapists and paedophiles who had the right to marry, but he couldn't,” she writes. “This is absolutely not fair.” Opponents and supporters of same-sex marriage have urged members of the public to lodge submissions to the Senate Legal and Constitutional Affairs Committee, which has set a deadline of today for public feedback.