The bras have been a feature of a farm fence just north of the Cardrona Alpine Resort entrance for about 15 years.
Operator of The Cardrona Horse Trekking and Quad Biking tours business behind the fence, Sean Colbourne, told the Otago Daily Times last night he was disappointed a ''sneak thief'' was prowling around at night with a pair scissors taking the bras, many of them left by passing tourists.
''The next time someone tampers with it we will charge them with theft and trespass.
''We're not quite sure who's doing it or what their agenda is.
''I just find people sneaking around in the middle of the night with scissors is a little bit mischievous.''
Mr Colbourne said he had not complained to the police but was looking at ways to make the bra fence more secure.
One possibility was to move it further away from the road on to the land where his business operates.
Mr Colbourne said he was bemused by the amount of genuine interest shown in the bra fence by tourists who stopped to take photos.
He was one of those who added to the fence when bundles of bras were sent to the valley.
''It's a bit of a frivolous fun,'' he said.
The original bra fence was started by Cardrona identity John Lee and revived by son Sam Lee last year, in memory of his late girlfriend, Danielle Cook, who had enjoyed the fun of contributing to the bra fence.
Supporters have always maintained it is a bit of fun that puts the Cardrona on the map.
Opponents have raised concerns about road safety.
