The new Public Service Commissioner Sir Brian Roche has joined coalition voices in criticising a health official as "unprofessional" for characterising some ministerial work as "crap" in an internal email.
It comes after the Director-General of Health Diana Sarfati emailed all ministry staff stressing the need for professionalism in all communication.
The Green Party responded with outrage on Wednesday, accusing them both of caving to coalition pressure and throwing public servants under the bus.
In a statement issued to RNZ, Sir Brian said the Ministry of Health was right to apologise to the government for "the unprofessional nature of the [staffer's] comments".
"We must always, regardless of the circumstances, be professional and politically neutral and think carefully about how our behaviour might be perceived.
"What happened is a lesson for all of us in the public service to reflect on and learn from."
In a ministry-wide email on Tuesday afternoon, Sarfati invited staff to reflect on "what it means to be a good public servant". She said they had a "duty to uphold high standards of integrity and conduct" to maintain New Zealanders' trust and confidence.
"I want to take this time to remind all kaimahi about the importance of professionalism in all our communication. This includes emails, text and the way we speak to our colleagues.
"We are privileged in our roles to, at times, be given access to sensitive or confidential information and it's vital that each of us behave in a way that retains the trust of Ministers, Parliament and people of New Zealand.
"Trust is hard earned and easily lost."
The email follows strong criticism of the ministry's recent conduct from the coalition: Associate Health Minister Casey Costello accused officials of undermining her work, and Prime Minister Christopher Luxon said they had not served Costello well.
The Greens: public bosses are caving to the coalition
Green Party public services spokesperson Francisco Hernandez told RNZ that the message being sent by both Sir Brian and Sarfati was deeply worrying.
"A lot of the top bosses are caving," he said. "Instead of standing up for their employees, they're standing up for their ministers."
Hernandez said public servants should be able to speak frankly in internal emails - and there was no need for the director-general to apologise.
"If anything, they should be apologising to the staffer for the way that they've handled things, in the way that they've left her out to dry."
Labour's health spokesperson Ayesha Verrall, on Tuesday, also said an apology was unnecessary.
"When did it become wrong, in internal emails, to call something that is crap, crap? That's what free and frank advice is," Verrall said.
Public Service Association national secretary Kerry Davies told RNZ the staffer was simply doing her job in calling out substandard work.
Davies said Costello's response was outrageous and unacceptable.
"It ends up having a chilling effect on all officials. It sends a message that if you provide free and frank advice, then you're likely to be called out by your minister and, dare I say, the prime minister, publicly."
Davies said the PSA would write to the Public Service Commissioner to lay out its concerns. On Wednesday morning, the Commission told RNZ it had yet to receive a letter.
Ministry correspondence, first revealed by 1News, showed a top health advisor criticised the quality of information provided by Costello to justify cutting tax on heated tobacco products.
The official wrote: "It's not so much that all of the studies are crap... [but that they are] selective... not up to date... and don't represent current evidence".