It's been blamed for one death and has led to some school students being disciplined.

But Prime Minister John Key is now part of the "planking" fad after photos appeared online of him in the background of his son's plank.

The photo shows Mr Key's son, Max, performing the internet craze while the Prime Minister stands behind him.

Fifteen-year-old Max's picture - called the "PM plank" - has been uploaded to the Planking New Zealand Facebook page, where people have left comments applauding his efforts.

"This a Key Plank," one person posted.

Jay-Jay Feeney, from The Edge radio station, commented on the picture: "Brilliant! But your dad is doing a vertical plank. He needs to be horizontal."

One person labelled the photo a "National plank" and others hoped Mr Key would upload pictures of himself planking at the Beehive.

A spokesman for Mr Key said he had "nothing to say" about the photograph.

The planking craze has swept the world, and in New Zealand, more than 12,500 people have joined the Planking New Zealand Facebook page.

NetSafe chief executive Martin Cocker said the Prime Minister's photograph showed how popular the fad had become.

But as long as people performed their planking stunts in a sensible way, he did not have a problem with it.

"It's when people try and get a picture which is more and more risky and exciting - that's where the risk is."

Planking has been blamed for at least one death after a Brisbane man slipped and fell seven storeys while planking on a narrow balcony railing.

A New South Wales man is in a coma after the car he was planking on top of stopped suddenly, sending him flying on to the road.

Last week, several high school students were disciplined for taking planking stunts too far. One was filmed stretched across a rail line in South Auckland as a train approached, a Tauranga Boys College student was photographed lying on another railway track, and a pupil of Carmel College on the North Shore was snapped on top of a concrete pillar.