The Danish Christmas Tree Growers Association has been charged with rigging prices for the yuletide evergreens.

The prosecutor for serious economic crimes in Denmark, the continent's leading exporter of Christmas trees, laid the charge this week after a year-long investigation.

No date for a trial has been set.

The charge comes after warnings from Denmark's competition authority in 2001 and again in 2005.

It urged the Christmas Tree Growers Association to stop givingmembers wholesale price guidelines, which the authority saw as being aimed at preventing growers from undercutting one another.

The cost of Christmas trees is up by about 20 per cent in Europe this year. The association blames a shortage of trees for the substantial price hike.

"We have been charged and I will not comment on the case until a trial begins," said Kaj Oestergaard, the association's manager.

Danish growers cut down about nine million fir trees eachyear, of which about 85 per cent are sold abroad, mostly in Germany, Britain and France.

The wholesale price for a Nordmann fir, the most popular Christmas tree, ranges from the equivalent of $8 to $57, depending on size and shape.