The Greens' Metiria Turei is calling for the Adoption Act to be changed to allow adoption by same-sex couples.
So bring a Member's Bill on the subject already. The Greens are already running out of bills to put in the ballot (the Green ballot mojo has its disadvantages sometimes), and this would give them another issue to campaign on. In addition, it has a high likelihood of passing. As I pointed out last year, same-sex adoption is the progressive issue with the best chance of passing this term. As a basic issue of equality, only the most retrograde of Labour MPs would oppose it, and it would have universal support from the Greens. According to the profiles at NZVotes, two National MPs (including John Key) were willing to publicly back such a bill - and this did not include answers from National's traditional liberals such as Pansy Wong, Clem Simich, and Katherine Rich. Add in Brian Donnelly (who really seems out of place among the dinosaurs of the NZ First caucus), and it sems there would be a majority there, without having to consider the unreliable ACT vote, or the position of National's new (and therefore unknown) MPs.
The only worry is that United Future would threaten to bring down the government if they backed such a bill - but I don't think that forcing them to make such a statement publicly would hurt in the slightest. They'd immediately be tarred as a party of fundamentalist bigots intent on imposing (their peculiar version of) "God's Law" on the rest of us - and such parties have never really done well electorally in New Zealand.
The current situation is blatantly discriminatory, and for no good reason. Gays make as good parents as straights, and that should be the only question in adoption decisions. The sooner the Adoption Act is amended, the better.