Prime Minister John Key has appeared in a video laughing, joking and poking fun at himself during a session with Australian comedian Peter Flaherty.

Flaherty's character Shaun Wayne, who bears a remarkable resemblance to cricketer Shane Warne, ambushes Key in a car for the unscripted, seven-minute piece.

Key tells Wayne he works for the government – the Aussie has no idea he is talking to the country's leader.

The subject of the government's new BMWs become a reason to laugh. "They're nice. They're good value," Key says in the video.

"I heard that nice prime minister talking and he didn't have a clue what was going on. He bought 34 of them and he didn't have a clue what was happening. "Honestly, the things they try and whip through, sometimes it's beyond me."

The video was taken during Napier's Art Deco Weekend last month as part of a $100,000 campaign to market the city to tourists from the east coast of Australia.

Napier Mayor Barbara Arnott was worried Key wouldn’t give it the go-ahead once he saw it, but the PM approved its release.

The council hopes the video will go viral on social networks to back up a big tourism campaign in Australia.

Watch the full video here