Prime Minister John Key has admitted the Government sometimes delays releasing official information right up to the deadline if it is in its best interest to do so.
Legally, it must respond to requests as soon as reasonably possible.
Mr Key's admission comes just days after the release of official advice on child poverty which Radio New Zealand requested 17 months ago.
Mr Key has always maintained that when it comes to requests for official information, his ministers act within the law.
But he has now revealed a strategy which appears at odds with that.
"Sometimes we wait the 20 days because, in the end, Government might take the view that's in our best interest to do that," he said.
Legally, ministers and government departments must respond to a request as soon as reasonably possible and no later than 20 working days.
Chief Ombudsman Dame Beverley Wakem said they were not allowed to delay right up to that 20-day deadline for political purposes.
"It's pretty clear. It couldn't be much clearer than that... As soon as you have made a decision as to whether you're going to respond to the request or how you're going to respond to it, you ought to convey that."
However, there are no sanctions for deliberately delaying the release of official information.
Labour's acting deputy leader, Annette King, said Mr Key's comments were disturbing.
"There's been a growing arrogance by this Government that they can do exactly what they like with official information... it borders on trying to undermine a fundamental tenet of democracy," she said.
Green Party co-leader Metiria Turei said the culture was poisoned right from the top.
"If the Prime Minister won't follow the law and instead will use this for his own spin purposes, then of course all his other ministers will do the same... they will release information when it's in their best interest and they will withhold it when it's in their interest and the public be damned."
Mr Key said his Government did not treat official information requests any differently from previous governments.
Dame Beverley is to begin a wide-ranging inquiry into how the Official Information Act is being used late next month.
She stressed she had not heard of ministers delaying responses within the 20-day timeframe but said it would be hard to prove.
"That's the sort of thing that I expect we'll pick up as we consult. And we'll be consulting widely, including media, so that we can identify any blatant or egregious attempts to dodge responsibility, but... I'm not aware of any of that sort of thing going on at all."
Dame Beverley said her review would not be a witch hunt but would look into agencies' practices and highlight any misinterpretations or difficulties.