Key Points:

The Advertising Standards Authority has received a complaint about a billboard which allegedly shows a thief stealing electrical transformers from an Auckland advertising company.

When efforts to track down the thief failed, OTW Advertising decided to mount the billboard with a photo of the man caught in the act along with the words: "Who is this thief? $500 reward."

The photo of the man, wearing a hi-visibility vest, was among a series taken by a witness who says he watched as the man dismantled and stole 15 transformers used to light the billboard, which were worth about $5000, on October 12.

The billboard strategy has attracted international media attention and generated more than a hundred responses - most of them supporting the company's decision.

But a disgruntled member of the public has complained to the Advertising Standards Authority, apparently over the fact that the billboard breaches the suspect's privacy by calling him a thief before it has been proven in court.

"We're trying to get it dismissed but if it's upheld as a legitimate complaint then I have to fly down to Wellington and attend a hearing and see what happens," Mr Venter said.

"If the complainant's view is seen to be fair then we have to pull it down."

Mr Venter said he had received more than 100 text messages about the theft - most of them supporting the company's decision.

About 10 text messages had identified one person whose name had been passed on to police.

However, Mr Venter would not reveal the thief's name "because it just doesn't feel right".

"The police haven't released his name so we don't want to either."

Police have been looking for the man at several addresses around Auckland where he is believed to have been living but believe he has gone to ground because of the publicity.

Mr Venter said when the thief was caught he hoped to put the words "nabbed" or "gotcha" over the billboard.