The UK is the world's third largest importer of illegal timber, according to a report from conservation body WWF.
The UK spends £712m a year on illegal timber, WWF says
The charity has called on ministers to press for European legislation to prevent the import of illegal timber.
WWF says most illegal timber, wood from trees felled against local regulations or exported without duty being paid, came through Russia and Scandinavia.
The government said it was committed to cracking down on illegal logging and associated business.
'Licence to wreck'
WWF estimates that the UK is spending £712 million a year on illegal wood, much of it coming through Sweden, Finland, Estonia and Latvia.
According to Beatrix Richards, the WWF's head of forests, the figures are based on "looking at the anomaly between legal exports from a country and total recorded imports from the country".
Defra, the department responsible for environmental policy, has insisted that trade in illegal timber is "unacceptable".
"The UK is leading the world in public timber procurement policies and this government is committed to tackling illegal logging and its associated trade," it said in a statement.
Greenpeace is vocal on the issue
Greenpeace, which has held demonstrations at government buildings it claims are being renovated using illegal timber, criticised the official response to the problem.
"The UK government has refused to bring in laws to ban the import of illegal timber into the UK," said its spokesman Ben Ayliffe.
"Instead it has approved various timber certification schemes that supposedly guarantee "legal and sustainable" timber, but in reality are nothing more than a licence to wreck ancient forests."