A top government watchdog wants an assurance ministers aren't flouting the law when dealing with requests for official information.

Photo: RNZ

Chief Ombudsman Peter Boshier has written a letter to Prime Minister Bill English after the Transport Minister's office tried to stop KiwiRail from releasing a report.

Photo: SUPPLIED

He said such incidents risked eroding public confidence in the government and democracy.

The Official Information Act sets out the rules for responding to requests and is designed to keep ministers and officials accountable.

Mr Boshier said he had asked Mr English to confirm his ministers were committed to the Act and understood their obligations, particularly in an election year.

"It's so important that we get this Act flowing better than it has been and it hasn't necessarily flowed that well.

"And that's why I've used this as an opportunity to exhort the Prime Minister to help me and support me in getting the roles crystal clear."

He said "leadership from the very top" was necessary to guarantee government accountability and openness.

"We are coming down increasingly heavier where we see instances where the Act is not being compiled with - and in some cases, where it's been flouted.

"I think there's an understanding that we mean business."

New Zealand First last week released emails which show Transport Minister Simon Bridges' office urged KiwiRail not to release the business case for a proposed new rail line in Auckland.

His staff pushed back even after KiwiRail insisted it legally had to be released.

Mr Boshier wouldn't comment on the specific case, saying he had yet to properly investigate it, but said he would look into it if someone made a formal request.

"There's no doubt in this case that if it was felt there had been an error and we were asked to investigate, we would do so."

New Zealand First leader Winston Peters last night lodged a request asking that Mr Boshier do just that.

He said the government had been acting in a "very smug and arrogant and interventionist way".

"They've been outed breaking the law, so to speak, and carrying on as if accountability doesn't matter."

Photo: VNP / Daniela Maoate-Cox

Mr Bridges, though, defended his office's actions and said his officials' objections were valid.

"[The document] is a very early draft, materially wrong in a number of respects, in relation to something that will need to be decided by government.

"Historically, those things have not been released in quite a number of cases."

He said, nevertheless, the document now either would be or has already been released.

Mr Bridges said he personally had had no knowledge of the email exchange.

Mr English said in a statement he expected all ministers and their staff to comply with the law.

A spokesperson said his office gave Mr Boshier that assurance last week.