A woman who got Simon Bridges to sign a nang says the politician was "blissfully unaware" of what he was putting his name on to.
An image of the cream charger hit social media on Thursday with the Bridges' signature scribbled across it.
The canister contains nitrous oxide, commonly used for pain relief, whipping cream and in recent times has made a resurgence as a way to get a quick high.
The gas can also reportedly cause a drop in blood pressure, fainting and heart attacks.
A picture of the signed nang was posted for sale to the Facebook page for Otago University's student magazine Critic Te-Arohi.
"NANG SIGNED BY SIMON BRIDGES," read the caption. "Serious inquiries only."
Another picture of the whipped cream canister was posted on Twitter by a woman who claims she told Bridges it was an urn.
"Got my nang signed by the blissfully unaware Simon Bridges," she wrote.