The Government is rejecting a call from National to set up a cross-party mental health group.
National's Spokesperson for Mental Health, Matt Doocey, wrote to Health Minister David Clark in July suggesting collaboration.
But now Mr Clark has responded, telling him to wait until a major health inquiry is over.
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Led by Professor Ron Paterson, the Inquiry into Mental Health and Addiction is due to report back by the end of October.
"I really don't think now is the time for a talk-fest among politicians when we've just had a robust enquiry due to report back shortly," Mr Clark told RadioLIVE on Thursday.
In his letter to Mr Doocey, Mr Clark criticised what he sees as National's previous indifference to the issue while it was in power.
"In the last decade the number of people accessing public mental health services has increased significantly," he wrote.
"Last year thousands of New Zealanders wrote letters and signed petitions calling for an inquiry into mental health and addiction. This was resisted by the then National Government."
Mr Clark says any collaboration with the Opposition will be best done in select committee.
"My view is that cross-party work is best done at the Health Committee in the first instance, or more broadly with other interested Parliamentary colleagues after the Inquiry has reported," he told Mr Doocey.
"In either case, I would encourage you to discuss these matters further with Ms Louisa Wall, Chair of the Health Committee."