A former top Beehive staffer used his personal email account to conduct official business.

A former top Beehive staffer used his personal email account to conduct official business - meaning at least one document was not released under the Official Information Act when it should have been.

That document - which lobbied for changes to climate change legislation - was sent by Fonterra to Matt Burgess, who was the prime minister's chief policy adviser at the time.

The revelation has drawn a stronger reaction from the Prime Minister than his response following reporting by RNZ last month the same document was given in hard copy format to the same staffer, which Christopher Luxon's office had no record of.

Luxon now says it does not meet the standards expected of staff in the Beehive and undermines public trust and transparency.