A Law Commission review of the issue has been put on hold because of other government priorities.
Mr Chauvel said the High Court had ruled almost anybody in New Zealand could adopt under the current law - but not gay couples.
He said the High Court had said you could adopt a child if you were married, single or in a long-term heterosexual relationship, but probably not if you were in a civil union. "The whole law is well and truly out of date."
Mr Chauvel said the policy would also require New Zealand to advocate strongly for the abolition of the death penalty in other countries for consensual same-sex sexual activity.
"It's something we've been a bit too silent on in the current Government and it's something I'd love us to be more active on."
It would also require schools to act to prevent anti-gay bullying and publicly report on the success of such policies in schools.
Discussion of the policy prompted Act candidate Stephen Whittington to accuse some in Labour of being homophobic after a meeting of the gay community in Wellington this week.
Mr Whittington had argued that despite Labour's policy, two of its own MPs - Trevor Mallard and Clayton Cosgrove - had referred to National MP Chris Finlayson, the Attorney-General, as "Tinkerbell" in the past in a clear reference to his sexuality.
Mr Whittington sent out a statement claiming Labour's Grant Robertson and Charles Chauvel had tried to ignore it rather than denounce it by denying the MPs were homophobic.
Mr Chauvel said he had never heard anybody refer to Mr Finlayson by that name "and if I did hear it, I would tell them that was unacceptable".
Mr Robertson said he was aware of the nickname but did not believe Mr Mallard was homophobic, saying he had helped drive homosexual law reforms.
Mr Robertson said the issue arose after a member of an audience described Act Epsom candidate John Banks as homophobic and Mr Whittington was trying to defend him.
The parliamentary record shows Mr Cosgrove called Mr Finlayson "Tinkerbell" in July 2009, after Mr Finlayson referred to him as "Mini-Mike" - a reference to former PM Mike Moore - and then "Mr Comb-Over".
Mr Mallard is also recorded as saying, "Tinkerbell, can you settle down?" in 2009 after an interjection from Mr Finlayson.