''Children need a mum and a dad,'' Stuart Robert told Parliament last night, addressing a Bill that changes many Commonwealth laws to remove discrimination against same-sex couples and their children.

The Opposition does not oppose the measure, but has moved an amendment urging a Senate committee to ensure it doesn't devalue marriage.

Mr Robert said a study in Norway and Sweden, which introduced similar legal protections, found gay male unions were 50per cent more likely and lesbian unions 167per cent more likely to separate in the first eight years.

An Australian study showed heterosexual couples' children generally developed better.

Mr Robert said ''deliberately creating a child to be placed in a homosexual relationship is irresponsible, considering all the available evidence''. AAP