Former broadcasting minister Jonathan Coleman has admitted using incorrect audience figures for the soon-to-be-defunct TVNZ7 but says the free-to-air channel was to be scrapped anyway.

Those campaigning to save TVNZ7, which is due to turn into a TV One Plus One channel next month, say the error has contributed to the demise of New Zealand's only commercial-free, public-service television station.

In April last year Dr Coleman said TVNZ7 attracted about 207,000 viewers a week, compared with the 600,000 people who tuned in nightly to One News, and the Government would not be putting new money into the channel because it was not a high priority.

He was questioned about the figure earlier this year after a report on TVNZ7's own programme Media 7 said it was wrong because Dr Coleman had divided a monthly figure by four. Audience data was only collected once a month and weekly audience numbers were much higher, it said.

At the time Dr Coleman said the figures were provided by officials or by TVNZ itself.

However, papers released under the Official Information Act show the only figure officially provided to Dr Coleman was that Channel 6 and TVNZ7 together had a monthly audience of 2.1 million.

That figure was contained in a Cabinet paper he approved in February last year which said the Government would not extend its funding of $79 million over six years, $70m of which was offset by a special dividend paid by TVNZ.

Yesterday Dr Coleman said an official from the Culture and Heritage Ministry or someone in his office had verbally provided him with a breakout figure.

"I can't remember exactly but at some point we decided it was 200,000 per week.

"That formula was not correct but at the end of the day that was not central to the argument."

The decision to axe TVNZ7 was made on the basis the funding was for only a set period, he said. The channel had been set up on the understanding it would be self-sustaining when that funding ended.

"When it came to the end of the funding period there was no plan for how they would be funded in future."

Labour's broadcasting spokeswoman, Clare Curran, said the incorrect figure had been "extremely damaging".

"The theme that TVNZ7 has got very small audience figures has been pushed by all Government ministers and so therefore it's not going to be missed."

Labour is running a campaign to save TVNZ7 and Ms Curran said public meetings around the country were attracting hundreds of people.

Officials took steps to ensure Broadcasting Minister Craig Foss, who took over the portfolio in December, would not make the same mistake.

In a memo in March, officials warn: "Cumulative figures cannot be divided to provide weekly audience figures as people only get counted once in the month, so a straight division of four will misrepresent viewer numbers."

The memo also notes TVNZ7's cumulative monthly audience increased to 1.47 million in the week beginning December 25, up from 1.40 million the month before, and a big rise on 863,100 a year earlier.

- © Fairfax NZ News