The Labour Party says Prime Minister John Key has either had a brain fade when making his latest comments on the drinking age or has simply not told the truth.
Mr Key told reporters on Wednesday that he had voted for the age to be raised to 20, when in fact he voted for it to stay at 18.
In two conscience votes, he voted firstly for the split-age proposal, then in the final vote to keep the age at 18.
On Wednesday, Mr Key was asked for his response to a poll finding 57% of people thought Parliament got it wrong by keeping the status quo.
He responded by saying he wasn't surprised by that result, which is why he had voted to raise the age to 20.
Labour's deputy leader, Grant Robertson, says he can't understand why Mr Key would make those comments.
"Clearly it's either another brain fade from the Prime Minister," Mr Robertson says, "or he's simply not telling the truth - and I think New Zealanders deserve a bit better than that from the Prime Minister."