Green Party co-leader Metiria Turei was outraged that the air force "ferried" Mr Key to what she called exclusive events.
Mr Key used the Iroquois on Saturday to attend the Hamilton V8s then a black tie dinner at the Royal Auckland Golf Club in Otahuhu, Auckland.
"The Green Party has no problem with the Prime Minister using the air force in order to help out in emergencies or for important government business," Mrs Turei said.
"We do have a problem with the Prime Minister commandeering the New Zealand Air Force so that he can get snapped at the V8s before heading off for an exclusive knees-up at the Royal Auckland Golf Club."
A spokesman for Mr Key said he flew to the V8 event from Mechanics Bay to the Waikato Stadium mid-morning. The return helicopter flight back to Mechanics Bay was scheduled for 3.30pm to 4.30pm but arrived 15 minutes late.
The next event was a celebratory black tie dinner for granting royal status to the Royal Auckland Golf Club, at Otahuhu. He had to go home to change for the event and was due there at 7pm.
"The decision was made to use helicopter because of concerns about traffic issues at major events -- that is, the V8 event in Hamilton. It was believed that transport issues would have meant he could have been late for the next event, which was unacceptable because the protocol is that he cannot arrive later than the Governor-General.
"With regard to air force transport generally, we seek to balance our needs around transport. When we use the air force, more often than not it's because that's the best logistical option we have that fits with the timing requirements of the Prime Minister's schedule."
