(Reuters) - Canada is tightening the rules for producing its popular icewine, a sweet dessert wine that is only made in cold climates, to crack down on fraudsters who sell mislabeled bottles that don't make the grade. 

In regulations published this week, the Canadian government said any bottle labeled and sold as icewine must be made only from grapes that have frozen on the vine.

Some producers of counterfeit ice wine add artificial sweetener to mimic the wine's sugary taste, while others freeze grapes after they have been picked.

Even some Canadian apple ciders have been marketed as apple icewine, Dan Paszkowski, who heads the Canadian Vintners Association, said on Wednesday.

"They can produce a fine wine, but that wine should not be allowed to be called icewine," Paszkowski said.

Canada is a major player in the international market for icewine, thanks to a reliably cold climate. It exported 223,000 liters in 2012 and sold 180,000 liters domestically.

Ontario already had rules on what constitutes icewine, but the changes apply across Canada.

Because the frozen grapes only yield a tiny amounts of sweet liquid, the dessert wine has a high cost and a high price. Grapes are left on the vine until the temperature falls to -8C (18F) over a prolonged period, and usually harvested overnight.

"It's liquid gold," said Paszkowski.