Helen Clark's chief press secretary, Mike Munro, and a number of others people complained about the broadcast.
The allegations of a cover-up over contaminated corn dominated the run-up to the general election on July 27.
The Government strenuously denied there was any contamination and if there was it had been at such low levels it was scientifically impossible to detect.
The authority said it declined to determine or uphold other aspects of the complaint, including the conduct of the interview.
It also regretted that it had taken a year to come to a decision.
However, matters of process mainly raised by the broadcaster had required a number of interlocutory decisions before it could address all of the complaint.
The decision itself runs to 92 pages and asks the parties concerned to make submissions about the punishment that should be handed down.
These range from nothing through to airing an apology or having advert-free programming.
Mr Munro said Helen Clark was happy with the decision.
Among other matters the authority upheld that:
* The programme was unbalanced on the issue of Government accountability
* Gave different treatment of Miss Clark and Mr Hager
It did not uphold complaints about the style and conduct of the interview and declined to make decisions on scientific facts in dispute.
"The authority upholds a number of aspects of some of the complaints that the broadcast was unbalanced, that it was inaccurate and lacked impartiality and objectivity, and that it was unfair," the report said.
- NZPA
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