"Illegal logging destroys the protective function of forests, increasing risk of natural disasters such as floods and landslides and leads to deforestation, one of the main causes for climate change," WWF forest policy officer Anke Schulmeister said in a statement.

Illegal tree cutting also pushes timber prices lower, hurting companies, countries and local economies, she added.

In 2006, the EU imported some 30 million cubic metres of wood or wood products that were of illegal origin, mainly from Russia, China and Indonesia, according to the WWF report "Illegal Wood for the European Market."

"WWF is calling for additional legislation at the European level to stop the trade in illegal timber and wood products within the EU," the group said.

The bloc needs to "put the onus on companies which trade in wood products to demonstrate compliance with the law" and show that their raw material comes from legitimate sources, it added.

Finland, which is home to several of the world's largest paper makers, is the biggest importer of Russian wood to Europe, but legitimate imports into the Nordic country have fallen since Moscow began gradually ratcheting up export duties in 2006.

According to WWF, some 3.7 million cubic metres of Russian roundwood was illegally imported into Finland that year, corresponding to about 14 percent of all EU wood imports "based on products derived from illegal sources."

The conservation group acknowledged that some large Finnish forestry groups have gone to great lengths to exclude illegal wood from their production chain. However, it maintained that other companies with limited ability to exclude such timber "continue their operations, seemingly doing virtually nothing to improve."

WWF meanwhile listed Britain, Germany and Italy as the largest importers of furniture and other wood products from Asia, including China and Indonesia, estimating that about 40 percent of these products originated from illegal logging.