You might not guess it flying west from Manaus in a small plane but the mighty Amazon forest is in jeopardy. Thirty years ago only one percent of the Amazon forest had been cut down. Today a quarter has disappeared.

Now previously untouched areas in the very heart of the forest are being felled, and, as elsewhere, most of the logging is illegal.

The logging takes place during the dry season, which has just begun. Later in the year when the rains come and the floodwater rises the logs are floated out of the forests and down the rivers to saw mills, many of them in Amazonia's biggest city, Manaus.

I came across a raft of 120 or so illegally cut logs hidden in a secluded inlet on the Jurua River.

Milton Casara, head of the Brazilian Environment Agency in Amazonas state confirmed that they were illegally logged. He says well over half the wood logged in the state is illegal.

Anonymous middlemen approach the poorest villagers who live along the region's rivers and offer them pitifully small amounts of money to pick out the biggest trees.

"The exploitation of local populations is increasing", he says, "and its leading to a greater degree of poverty here. It's a fundamentally unjust relationship...I would even describe it as inhuman".

Sergio Lauria, the State Prosecutor for Manuas, says even catching the dealers who buy the illegal wood will not solve the problem.

"By attacking these middle men there is no way that we are getting to the crux of the problem," he says.

"You could compare this to drug trafficking for example. Tackling the dealers will never eradicate the problem of drug trafficking."

This is not just a question of law enforcement, but a political battle.

The big logging companies are pressing for permission to exploit the forest here in the previously untouched heart of the Amazon. Ranged against them are environment groups like Greenpeace, and indigenous people such as the Deni.

The Deni, who live in a village on the Xerua River, oppose plans by a large timber company, WTK, to log land it has bought nearby. They rely utterly on the forest and say their hunter-gatherer way of life would be destroyed by proximity to the logging.

WTK's subsidiary Amaplac is among the companies in Manaus turning Amazon timber into plywood, although there's no evidence the company is involved in any illegal trade. Amaplac exports much of the plywood going to Britain, which arrives in regular shipments at Tilbury docks.

From here it is delivered to builders' yards, like the one in London where I bought a sheet of Amaplac plywood for £15 ($23). It's hard, waterproof and not too expensive and is used for things like boxing in pipework and laying concrete. Hardly glamorous end uses for some of the world's most precious forests.

The destination of the wood increases the pain felt by people like Paulo Adario, Greenpeace's Amazon campaigner. He points out that the tropical rain forests are thought to contain more than half of all species.

"In just one hectare here we have 500 species of trees," says Mr Adario.

"In Europe you can count maybe five or six. It's incredible, the biodiversity here is really something, and we are destroying it without giving ourselves time to learn what we are destroying."

Greenpeace reserves much of its criticism for the richer industrialised countries, like the UK, which it believes are guilty of wilful inaction. The G8 group of industrial nations agreed at a summit in Denver three years ago to support what it called a practical action plan.

It includes "building capacity for sustainable forest management", and "eliminating illegal logging". Another summit the following year, confirmed the plan, but Greenpeace claims nothing has happened.

The government says little of the timber exported to Britain was illegally logged. Greenpeace questions whether the UK can be getting only the 40% of timber from Amazonas that was legally felled. Meanwhile campaigners are appealing to the wood buying public to consider themselves.

By Robert Pigott