UPDATED 3.51pm: Environmental groups are taking the Electoral Commission to court over a ruling on a climate change campaign.
Greenpeace, Forest and Bird, WWF and others launched the Climate Voter initiative last month.
But the Electoral Commission says the campaign counts as an "election advertisement", and is therefore subject to rules around wording of communications and spending restrictions.
Greenpeace says the ruling could gag grassroots advocacy groups - and the organisations are planning to take a freedom of speech test case to the High Court.
Greenpeace spokesman Steve Abel says it's become a free speech issue.
"Organisations that are advocating for anything, whether it's better cancer funding or milk in schools or lower taxes, the organisations should be able to do that without having to put a promoter statement on under electoral law."
Abel says the groups plan to fight that decision.
"There's a real risk that if it goes unchallenged, many advocacies or society groups could be effectively gagged from saying the things they'd like to say.
"In our instance it's climate change, which we think is a major issue that should be addressed by all political parties."