The Labour Party says a letter to an Iwi Leaders Group reprimanding its representative at the Climate Change conference in Peru is a heavy handed attempt at shutting down differing opinions.
Chris Karamea-Insley, the Climate Change Iwi Leaders Group's advisor, attended the meeting in Lima earlier this month.
Climate Change Issues Minister Tim Groser sent a letter to iwi leader Apirana Mahuika, unhappy with Mr Karamea-Insley's open cricitism at the meeting of the New Zealand government's climate change policy.
Labour's climate change spokesperson Megan Woods said it was hugely important there was a Maori voice and an honest voice at the table at international talks.
Mr Groser did not want to make any further comment.
Apirana Mahuika is expected to reply to the letter.