Associate Health Minister Casey Costello. Photo: RNZ / Angus Dreaver
Clarification: An earlier version of this story stated the Ministry had uncovered a staffer who leaked information. The Ministry has reported the staff member leaked information - RNZ cannot verify this statement.
The Ministry of Health says a staff member it claims leaked information to the media is no longer employed by the ministry.
RNZ last month reported on a Ministry document which showed the Associate Health Minister Casey Costello had requested advice on freezing the annual increase in tobacco tax.
That was despite Costello saying she had not sought advice on that.
In a statement, Director-General of Health Diana Sarfati - who heads the ministry - said the individual responsible for the leak had been identified after an investigation - and was no longer working at the ministry.
"Following the leak of confidential Ministry information to an external third party last month, the Ministry of Health began an investigation to determine how this occurred," the statement said.
"We can now confirm that the individual responsible has been identified and no longer works at the Ministry."
Sarfati said they took matters of integrity extremely seriously, and the ministry's job was to work to the direction of the government and any efforts to undermine that eroded public trust.
"I cannot stress how disappointing this has been."
In a separate statement, the Deputy Public Service Commissioner Heather Baggott said she supported the strong action, describing the leaking of official information as "unacceptable".
"Public servants who use their privileged access to government information to influence political debates undermine trust and confidence in the Public Service," Baggott said.
"The deliberate leaking of information is a political act which is incompatible with the neutrality requirements on public servants."
Costello apologised in Parliament last week for "any confusion", having previously said under questioning in the House she had not specifically asked for advice about freezing tobacco taxes.
Her initial explanation in Parliament was that she had not personally written the documents she sent to officials, and had asked for a "a range of advice", rather than specific advice.
After refusing an interview with RNZ's Morning Report, she had also told Newstalk ZB her office had gathered a range of policies, campaign positions and statements the party had made on the topic of tobacco in the past, but she did not know who collated it.
The leak is one of several to plague the coalition government since it took office.
Last week, a leaked Cabinet paper confirmed the government was looking into allowing more overseas investment for build-to-rent housing.
In January, the government confirmed a document about the proposed Treaty Principles bill was a memo leaked from the Ministry of Justice.
It followed a leak of a Treasury paper revealing the government had quietly suspended Regulatory Impact Analyses for some proposals in its 100-day plan.
An investigation into the earlier leak of Cabinet papers about Fair Pay Agreements also found an Oranga Tamariki staff member had sent a copy of that paper to an "outside source", which a spokesperson for the minister, Brooke van Velden, said had been a "national union organiser".
However, the Ministry of Business, Innovation and Employment said it was unable to find evidence of how the paper got to the media.