The percentage of Maori fluent in te reo fell by almost 5 per cent between 2006 and 2013, Census figures show, but Maori Television insists it is fulfilling its core purpose of boosting the revitalisation of the language.
General manager of programming Haunui Royal said the fact that te reo use appeared to be in decline, despite efforts to revitalise it, showed the challenge Maori TV faced.
Without Maori TV's efforts the language would be in an even more parlous state, he said.
A tracking survey by Te Puni Kokiri found 66 per cent of Maori said their desire to learn the language was increased by watching Maori TV.
"Nearly two-thirds of the people said, 'yeah, we watch it and it makes us want to learn our language'," Mr Royal said.
Pita Paraone, the acting chief executive of Te Taura Whiri te Reo Maori, a research unit created by the Maori Language Commission dedicated to the regeneration and revitalisation of te reo, said Maori TV had made great strides in promoting the language.
"I would like to see an increase in the percentage of programmes where the language is spoken," he said. "But it has made an enormous contribution to the revitalisation of te reo."
Mr Paraone questioned the accuracy of the Census results as the question about fluency had been poorly framed, with fluent speakers of the more formal language spoken on the marae, such as himself, answering "no" when asked whether they could hold a conversation about everyday things.
Mr Royal said Maori TV had also delivered on its second core objective to be relevant, effective and widely accessible.
The feedback the broadcaster had was that Maori were proud of it.
"The number one reason people come to Maori TV is that it makes them feel good about being Maori," he said. "We are very proud of that."
Maori TV played an important role in countering the frequent negative portrayal of Maori in mainstream broadcasting, Mr Royal said.
"The real power of a broadcaster is that daily message you send out. If you've got an underlying negative message there all the time what does that do for your children?
"Through Maori TV, Maori people have seen themselves play a much larger role in the national conversation than we did previously. That's about mana. Don't underestimate how important mana is to the whole revitalisation of Maori. It is not just about dollars in treaty claims."
Justice Minister Judith Collins has questioned the value of Maori TV, which receives more than $32 million of taxpayer funding each year.
Mrs Collins said most of the time when she tuned in the station was broadcasting "reruns of things that were running 30 years ago".
"I would like Maori TV to be considered one of our icons but at the moment it is not," Mrs Collins said.
"It's not dealing with the big issues. And when it does deal with them it is often seen not to be evenly handed in its treatment of them."
Q&A: Maori Television 10 years on
Former Herald and TVNZ reporter Maramena Roderick on Maori Television's 10th birthday celebrations.
Q: Maori TV is celebrating 10 years' operation - how do you think they're going?
The station should celebrate. It survived an onslaught of political posturing. It has endured continuing criticism from Maori, which, let's face it, can be ruthless because we take it so personally and hold everyone there accountable.
Q: What does Maori TV do better than mainstream channels?
Its programming is exceptional. The international documentaries are brilliant but the homegrown productions are inspired.
They are original, being recognised internationally but still ignored at home. Even after 10 years, many New Zealanders still see it as that channel over there for "those Maoris".
Then again, the whole rating system is peculiar. Has anyone ever met or even know of a Maori whanau who has a ratings box in their home?
Q: You wrote an opinion piece for the Herald about MTS on its opening in 2004 and asked whether MTS could ask the hard questions. Do you think it has?
News and current affairs are asking hard questions but not giving any new answers. Recently they've been replicating the style of others and whipping themselves into a frenzy instead of doing the basics of solid, investigative journalism which reveal far more valuable insights.