"There was a routine meeting held here in New Zealand last week. I wasn't involved in those meetings, I don't know the broad agenda of what they were talking about, I know the meeting was routine, I can't tell you exactly who was on the plane and who wasn't."
He said officials from other countries visited all the time and he did not know their travel arrangements, but leaving a marked jet on the tarmac did not indicate there was a high level of secrecy about it.
Labour leader David Shearer said Mr Key's apparent reluctance to find out more about the visitor raised suspicions.
"You either make a decision that you do not talk about who comes to the country, full-stop, or, if you are going to talk about it, you make sure you know who was in the country. I'm surprised he didn't know, as the democratic guardian of our intelligence agencies."