Shorten won't back deputy on gay marriage

Federal Opposition Leader Bill Shorten won't be backing his deputy's calls for a binding vote in the caucus on same-sex marriage.

While he supports marriage equality, Mr Shorten doesn't believe his MPs should be forced to vote for legislation to allow same-sex couples to wed.

Deputy Labor leader Tanya Plibersek will push the ALP's national conference in July to impose a compulsory `yes' vote.

The proposal has divided Labor members and Mr Shorten believes people have to be convinced, not forced, on the issue.

Labor's national conference four years ago voted to allow MPs a conscience vote on the issue, despite the party's platform being supportive of same-sex marriages.

Frontbencher Doug Cameron defended imposing a binding vote, saying it's not a religious issue but about the rights of every Australian to be treated equally.

But Labor MP David Feeney, who supports same-sex marriage, says a binding vote isn't the best way to "persuade the unpersuaded".

"I think going down a road where we are binding people to support legislation they're not minded to support, would be a terrible sidetrack," he told ABC radio.