A Television New Zealand manager has resigned following revelations that a company office was used to host at least one Labour Party meeting.
Documents also show that another staff member from TVNZ's Maori and Pacific Unit used the company email to organise Labour Party business.
The unit's general manager, Shane Taurima, contested the Ikaroa-Rawhiti candidacy for Labour and was considering doing the same for the Tamaki-Makarau electorate.
Documents leaked to 3News show a TVNZ office was used for a Labour campaign meeting in August last year.
The papers also show a staff member using the company's email to organise a Labour Party hui in January this year - which Mr Taurima was involved in.
Television New Zealand said on Monday it is investigating how such a serious breach of its editorial guidelines happened.
The company said Mr Taurima has been told he had a serious lapse of judgement and that editorial independence is paramount at any time - election year or not.
It is also investigating the involvement of other staff in the Maori and Pacific Unit and said it would respond appropriately.