The chief of the Environmental Protection Authority has denied the departure of the crown entity's controversial chief scientist had anything to do with the opinion of the associate Environment Minister.
The National Party is accusing Green Party minister Eugenie Sage of interfering with the EPA's staff and threatening its independence.
Scientist Jacqueline Rowarth resigned this year, after coming under fire from environmentalists and Ms Sage for comments that appeared to endorse irrigation.
Ms Sage's office in December forwarded a highly critical article about Dr Rowarth to the EPA.
The minister also said she met EPA chief Allan Freeth and discussed Dr Rowarth but has since retracted that, saying she had relied on memory and confused it with a meeting with Ministry for the Environment staff.
Recalled to explain to a select committee whether he had actually met with Ms Sage, Dr Freeth on Thursday vehemently denied Ms Sage had affected the chief scientist's resignation.
"At no time in the period covered ... did I have any discussions with minister Sage about Dr Rowarth," he said.
Pressed by National's Nick Smith about why Dr Rowarth had quit, Dr Freeth said she had been subject to "intense", "vicious" and "sustained" attacks on social media and "unhappy for many months".
The authority denies Dr Rowarth was pushed out and says she quit.
The email from Ms Sage was "not exceptional", had been instantly binned and an offer for a follow-up meeting was never taken up, he said.
Thursday's hearing came just hours after Radio NZ bosses fronted a select committee to correct the record over a meeting between head of news Carol Hirschfeld and Broadcasting Minister Clare Curran, which has also raised concerns about independence.