Marama Davidson facing backlash over supporting Whittaker's Te Reo branding

Backing te reo Māori on a chocolate bar has resulted in some backlash for Green Party co-leader Marama Davidson - and prompted a reminder for other ministers about the rules.

Davidson, who is also a minister, yesterday posted a photo of herself holding five golden-wrapped bars of Whittaker's milk chocolate to social media with an expletive-laden caption.

"F***en don't even like this flavour. But like @WhittakersNZ chocolate. And love #ReoMāori. @ArohatiaTeReo," she wrote.

Whittaker's faced backlash after introducing a limited-edition te reo Māori packaging for the milk chocolate block to support te wiki o te reo Māori, and Davidson said her post was intended to reject that racist criticism.

"I'm joining a movement that pushes back at racism that sort of grows around the blimmin' innocence of having a chocolate bar with a Māori name," she told reporters this afternoon.

"I will promote te reo Māori across all organisations who want to do that. We've got a trusted brand that has stepped to Māori language as a beautiful protected language and I'm really proud to play that part."

The trouble was the post could arguably be seen as promoting a product - something against Cabinet manual rules, though Davidson disputed that.

"It's been advised to me that there are some thoughts that I may have but I'm making it really really clear: I am promoting te reo Māori, I'm celebrating organisations who are also ... promoting te reo Māori and I'm also pushing back against the ridiculous racism that arose."

The chocolate bars were purchased using her own money, and she said the accompanying profanity was "very authentic and it's literally what I said".

She had not been contacted by the prime minister's office about the matter, but regardless would not be taking the post down.

Prime Minister Jacinda Ardern stopped short of saying Davidson's post was a breach of the rules, pushing the matter back to the Cabinet Office to deal with.

"I have asked and will ask the Cabinet office to just make sure they're in touch with the minister to be really clear on how those rules apply," she said. "I'll have the Cabinet office contact the minister and walk through with her the remedies and I'll give a bit of a reminder to ministers as well."

She said it would be along the lines of a reminder.

"Here we have companies embracing what is unique about New Zealand and there's a range of companies and brands that you can see are taking those steps and I think it's all part of our growth and our evolution as a country.

"I think it's quite clear to those who might be looking at that post that the minister's intention was to promote the use of te reo Māori, but we do have rules that are very clear around ensuring that you're not seen to specifically endorse particular products."

Te Pāti Māori co-leader Debbie Ngarewa-Packer said she had not seen the post itself, but she was "team Marama".

Labour's Willie Jackson also supported the support for the language, but said anything to do with the rules was for the prime minister to deal with.

"I mihi to Whittaker's and what they've done, and I'm not sure what the prime minister's doing but ... there were some real bad messages coming from a minority of people with regards to our language.

"I tautoko anything with regards to our language but if you're talking about the prime minister's decision you have to talk with her."

National's Chris Bishop said it was probably a breach of the Cabinet manual "in the most technical sense".

"Yes the Cabinet manual does say that ministers aren't allowed to endorse particular products, it's a very very technical breach.

"It's a relatively important principle that ministers can't use the station of office to endorse particular products but, look, I'm not getting particularly worked up about it."

He said ministers directed the use of public money, and the rule existed to avoid some products or brands having access and privilege others did not.

"On the other hand local MPs and list MPs like myself promote local cafes and local businesses and things like that - so there is a distinction between doing some thing in a Parliamentary capacity - promoting your electorate for example - and in a ministerial capacity."

He said expletives were "in keeping with Marama's style" but he had also "been known to let out the odd expletive in my own time".