In Burma, the ancient teak forests are being ripped apart...in Chelsea the precious wood is sold at the UK's top flower show

Exhibitors at Britain's biggest garden show, the Chelsea Flower Show, are selling hardwood from the unprotected rainforests of Asia, a trade that has been condemned by one of the country's leading environmental bodies.

Secret tape-recordings made during an undercover investigation by Greenpeace and The Independent found sales staff taking orders for teak garden furniture logged in Burma, whose brutal military regime is condemned globally. One trader said a teak table tucked at the back of his stand - behind more regular timber - had come from Burma because of "corruption". To the outrage of environmental groups, the Burmese military junta allows widespread logging of endangered rainforest.

The organiser of the show, the Royal Horticultural Society, backs the certification of timber to ensure garden tables and chairs on sale there are environmentally friendly and meet standards on child labour and human rights.

But several traders are exploiting the high profile of the Chelsea Flower Show to promote Burmese teak - even though the main certification body in the UK, the Forest Stewardship Council (FSC), refuses to certify the country's timber. One salesman claimed the teak tables on show at his stand were FSC-certified from Thailand, even though the FSC does not certify any teak from Thailand.

Exhibitors routinely get round RHS rules on sustainable timber by submitting documents for a "sample" of their products, while ensuring the main supply comes from cheaper sources, according to one garden furniture supplier who sells only legitimate timber.

Evidence about the availability of wood not proven to be environmentally or socially responsible comes amid rising concern over the fate of the world's great forests, which are under ever increasing threat. Yesterday the International Tropical Timber Organisation released figures showing that less than 5 per cent of the world's tropical forests are being sustainably managed.

To gather evidence The Independent and Greenpeace visited four stands at the Chelsea Flower Show yesterday morning fitted with secret tape-recording equipment.

At one of the stands, TFT Garden Furniture had a teak table at the back of its stand, which it was ostensibly using for administration. But when The Independent asked whether the company had any teak for sale the furniture was shown as an example of the teak that could be ordered in the styles of other tables on show.

Asked whether the table was "plantation" (made from certified timber), the salesman, Peter Doherty, replied: "This is not. It's Burmese teak. It's the best teak you can get because it's so corrupt out there. It's easier with this [FCS-certified eucalyptus furniture] than this type of wood [teak] which is hard wood, because it's so driven by demand. There's so much going out and there's just not enough people to produce the paperwork for it leaving the country and going here, there and everywhere."

He offered to sell the table for £799, saying: "It's hard to get FSC teak.

"The people in here [the Chelsea Flower Show] selling FSC teak, all they've done is buy a sample set and they send it off to the RHS, who organise this show and they say: 'This is our paperwork for it.' So it is hard for the organisers to make sure that all of the paperwork that comes in is for FSC."

The RHS said it did everything it could to ensure only certified timber was sold. Its brochure warns buyers to insist on certified timber: "If global timber resources are not managed in a sustainable way, the long-term availability of timber and the biodiversity which relies upon it, cannot be assured. Some tropical hardwoods are already under threat due to excessive harvesting."

Bob Sweet, the show's organiser, said they "disapproved" of exhibitors using the event to sell non-certificated timber from their catalogues.

Friends of the Earth estimates that the multi-million pound trade in hardwood garden furniture in the UK destroys 143,000 square kilometres of tropical rainforest annually.

A spokeswoman for the Forest Stewardship Council said that Burma's position on human rights made it "completely incompatible" with certification.

She said: "Unfortunately some companies, because of the RHS rules, will have on display one or two FSC lines to get into the show but the vast majority of what they sell will not be certified by us."

Greenpeace said: "The management of the RHS needs to take drastic action to ensure that immoral and environmentally-damaging logging like this is not available at the show."

Falling timber

* Between $10bn (£5.4bn) and $15bn a year is lost from developing countries' economies because of illegal logging

* Britain imports illegal timber equivalent to a forest three times the size of Luxembourg each year

* Global forest loss exceeds 12 million hectares per annum

* Up to 1.6 billion people depend on forests for their livelihood

* The EU imports around 45 per cent of all timber exported from the Amazon Basin

* Up to 8,000 square miles of the Amazonian Basin is being lost every year

* The UK has the third highest importation levels in Europe - behind Sweden and Finland

* Since 1980, an area of tropical forest bigger than India has been cleared for agriculture, mining and urban development