The group said labels on at least two tonnes of plywood were marked “red-faced mlh” (mixed light hardwoods) but testing found the face veneer to be bintangor, which it claims is sourced from threatened rainforests in Papua New Guinea (PNG).

Greenpeace said this represented “deliberate mis-identification of plywood” which was intended to avoid the environmental concern surrounding the bintangor species.

It has communicated its findings to The Timber Trade Federation (TTF), which is now conducting an investigation of the supply chain involved.

The Chinese-made plywood was being used in the parliamentary press area to protect floors, stairs and walls while refurbishment was carried out.

It is the fourth time in as many years that Greenpeace claims to have discovered the government using illegal and unsustainable timber. In July, campaigners occupied the roof of Admiralty Arch after identifying bintangor-faced plywood being used as hoardings around the site.

Biodiversity minister Barry Gardiner appeared on BBC2’s Newsnight programme to defend the government’s record on eradicating illegal timber.

The TTF recently warned its members that dealing with products containing wood from PNG was too risky due to the lack of credible evidence of legality.

“At this early stage it’s difficult to say what route this plywood has come through,” said TTF chief executive John White. He said the TTF was speaking to one of its members about the plywood.