Competing marriage-equality bills have marked the return of parliament in Canberra

The Opposition Leader is championing his bill to legalise same-sex marriage, while the Greens say their legislation has a better chance of cross-party support.

Bill Shorten introduces Labor's same-sex marriage bill Source: AAP

It comes as the Government tries to head off a potential internal split over who pays for the yes and no cases in a gay-marriage plebiscite.