NZSki CEO James Coddington said yesterday it was illegal for anyone to buy and try to use the personalised passes, which carry a photograph of the person who originally paid for it.
The second-hand passes, which originally cost up to $695 (early-bird), were being used by a "minority" of people trying to avoid the $87 daily lift passes.
But, he said, the consequences of getting caught were far more expensive, ranging from hefty spot fines of between $150 and $300 or, in some cases, being prosecuted.
"You get kicked off the mountain as well, so it's a very expensive alternative," he told the Queenstown Times.
"It can ruin your life - and your holiday. It's not worth it."
Mr Coddington said the practice of trying to use fraudulent passes emerged every season about this time and seemed to be a favourite habit of the 17 to 25-year-old age group, although he emphasised it was "definitely by a minority".
"They are not thinking [of the consequences], through," he said.
Four people were caught by what he described as "vigilant lift operators" at the Remarkables last Sunday and others were also found at Coronet Peak.
Some would be prosecuted.
"It depends on the level of co-operation. Generally, they are handed over to the police."
Last week, the Mountain Scene reported a 20-year-old German visitor had been charged with two counts of altering documents after he allegedly tried to change an old ski day pass and use it at the Remarkables earlier this month.
In a statement yesterday, Mr Coddington said NZSki wanted to tell people "in no uncertain terms" that it was not OK to sell passes.
"We take this offending very seriously, are well aware of the different ways of defrauding passes and are very good at catching offenders.
"The lifties are efficient at catching fraudsters, so we hope people will take this into consideration before illegally using fraudulent passes," he said.
