New South Wales MPs who plan to table same-sex marriage laws in state parliament say their bill can withstand a High Court challenge.

The ACT’s same-sex marriage bill passed in the Legislative Assembly yesterday, but the Federal Government is set to challenge the law.

Federal Attorney-General George Brandis has said he has received advice that the bill was “invalid by reason of inconsistency” with the Commonwealth Marriage Act.

Attention has turned to the New South Wales Parliament where a debate is set next week for a bill drafted by a cross-party group of MPs, including Labor’s Penny Sharpe.

Ms Sharpe says the draft has been scrutinised by constitutional lawyers and the proposed law creates a separate legal category for same-sex marriage distinct from the federal Marriage Act.

“Because the Federal Government only deals with marriage for heterosexual couples, our advice says that that would be perfectly consistent with the federal constitution,” she said.

“The ban on marriage for same-sex couples federally has left open the ability for states to legislate for same-sex couples and that’s what we intend to do.”

The bill will be debated in the Upper House late next week.