Opposition frontbencher Malcolm Turnbull has challenged his own party leader’s views against marriage equality, but insists civil union legislation is the best next step.

In a speech at Southern Cross University yesterday, he made clear he’s not convinced by arguments against same-sex marriage, but did not believe legislation for it would pass.

Noting the “hypocrisy” of the most “sanctimonious” traditional marriage defenders who quote the Old Testament, he added: “No matter how sinful some Australians may think homosexual acts may be, no matter how depraved and disordered or worthy of the fate of Sodom and Gomorrah they consider them to be, these are opinions which are not reflected in our laws today.

“Let us be honest with each other. The threat to marriage is not the gays. It is a lack of loving commitment – whether it is found in the form of neglect, indifference, cruelty or adultery, to name just a few manifestations of the loveless desert in which too many marriages come to grief.”

But Turnbull is unable to vote for marriage equality himself when the debate comes up in Parliament soon. Opposition leader Tony Abbott is not granting his MPs an individual conscience vote – they all most vote ‘no’ as a bloc.

This persuades Turnbull to advice the less controversial route of civil union legislation, which he realises will not be enough for many, but may be an important step along the path.

“While I am very doubtful the numbers are there to legislate for gay marriage in the Federal Parliament I think they are certainly there to legislate for civil unions,” he said.

“I think it would be a great pity if marriage is not able to be passed in the parliament and that opportunity to pass civil unions should be taken up.”

Malcolm Turnbull’s full speech is available to read online here.

Reacting to the speech, marriage equality advocate Alex Greenwich warns against civil union legislation.

“Wherever civil unions have been enacted they entrench discrimination rather than remove it,” he notes.

“Mr Turnbull should know better than to suggest civil unions as a way forward, especially given that his own electorate survey overwhelmingly rejected civil unions and endorsed marriage equality.”