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.
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.
Leadership on these issues comes from the top. John Key's office played fast and loose with the OIA, playing the hat game and refusing to answer requests, and this sent a clear message to other Ministers that that was how they were allowed (and expected) to behave. Bill English could send a different message by issuing a strong statement on transparency. But instead he has apparently simply told Ministers they are expected to "comply with the law". In other words, the current secretive and bullying practices will continue.