A laughing Prime Minister John Key has been shown making fun of himself and taking potshots at Australians in a comedy video posted online.

The Youtube clip, created to advertise Napier's art deco weekend, casts a dapper, 1930s-styled Mr Key with Australian comic and Shane Warne lookalike Peter Flaherty.

It shows him making light of Government controversies and saying Australians come to New Zealand to get the benefit.

He is particularly animated when the subject of his signing off the purchase of a multi-million dollar fleet of new BMWs comes up, saying he "didn't have a clue what was going on".

"He just bought 34 of them and he didn't have a clue what was happening. The things they try to whip through sometimes.

"It would probably be better if they were Holdens. I've had Holdens all my life."

Mr Key then starts ribbing Mr Flaherty and telling him not to try to claim a New Zealand benefit from Work and Income.

"I've heard they do that. They're off the plane, straight to the Work and Income office."