Greenpeace claimed that the plywood, protecting the base of the column during cleaning, was faced with bintangor from endangered forests in Papua New Guinea (PNG).

National newspapers reporting the Greenpeace protest said that the material had been supplied by MLM. However, Richard Lazenby, purchasing director of MLM Distribution Ltd, responded: “The Chinese plywood mentioned in press articles was supplied by MLM to a London-based merchant in early February 2006, and was correctly described as Chinese red-faced plywood on all documentation.

“This product is manufactured from 93% plantation poplar, with bintangor faces. A proportion of this plywood was then sold on again, to a contractor. The product was then incorrectly used in the context of a 100% certified sustainable product specification, on the restoration project.”

Mr Lazenby said that MLM stopped buying bintangor-faced products in April 2006 and added: “MLM travels regularly in China to audit current and potential suppliers and actively seeks to engage with mills who can demonstrate a commitment to achieving FSC certification.”

Following the Greenpeace protest, the Greater London Authority pledged to tighten up its timber procurement procedures and told staff to ensure all wood products are certified under the Forest Stewardship Council scheme, or its equivalent.

Meanwhile, The Timber Trade Federation has warned members that sourcing wood products made from timber from PNG is “high risk” and advised them to “avoid” it.