• Peter Collier, Western Australia's education minister, liked photo in 2011
• Stunt was popularised by comedian Chris Lilley in TV show Angry Boys
  

By Helen Lawson

PUBLISHED: 02:44 EST, 17 May 2013 | UPDATED: 03:14 EST, 17 May 2013

An Australian politician says he has learned a valuable lesson in social networking after he 'liked' a Facebook photo without realising that it showed a teenage prankster exposing himself. 

Peter Collier, the Western Australia education minister, said he clicked the 'like' button under what he thought was an innocent photo of the then-16-year-old in late 2011.

Collier apologised yesterday and said he had no idea that the teen, who was otherwise fully clothed and posing alongside an older man, was playing a prank commonly known as 'sneaky nuts'.

'At first glance it appeared to be a harmless picture,' Collier said in a statement.

'It was a silly mistake on my part. I only became aware of the actual content of the photo when shown by a journalist today.

'This obviously highlights the pitfalls of social media. I apologise if I caused any offence.'

The stunt was popularised by Australian comedian Chris Lilley's TV show Angry Boys, in which a character revels in ruining group photos by secretly exposing himself.

The prank has been a headache for some educators: Last year, administrators at a Catholic school in Canada scrambled to place stickers over a photo printed in all 1,300 class yearbooks of a student subtly exposing his genitals. 

The Australia incident did not attract attention until late last month, when the teen bragged on Twitter about fooling Collier, who he was friends with on Facebook.