WWF, the World Wide Fund for Nature, found more than 65% of local authorities in London did not check that their wood and paper products were sourced from threatened forests.

Its Capital Offence report revealed that nearly half of the London councils surveyed had no buying policy, and a third did not ask for proof that the products they bought came from certified woods.

"Authorities lack awareness of illegal logging," said Beatrix Richards, head of WWF's forest and trade policy.

"Councils account for around a quarter of the UK's total timber consumption and could use their purchasing power to make a difference."

Eight of the 35 London boroughs did not take part.

She called on all UK councils to join WWF's Forest and Trade Network (FTN), which helps businesses to source wood and paper products from well-managed forests.