Brazil is the world's biggest exporter of beef. Huge areas of semi-forested grasslands are being cleared to make way for cattle pastures to feed the global love of cattle meat. And Britain is one of the biggest importers.

Now, under greater scrutiny at home for their environmental and humanitarian sins, Brazilian beef barons are buying up land across the border in Paraguay – and bulldozing traditional Indian lands there. But, hey, it's all right, they say. Because, in among the ranches, they are creating nature reserves.

Are the ranchers going green – or engaging in flagrant greenwash to preserve their place on your plate? Now one company has been accused of invading the land of one of the few surviving tribal groups that are uncontacted by the outside world, and setting aside part of it for nature. And it has lined up the unlikely figure of Charlie Chaplin in its defence, bizarrely saying British-born "Chaplin would be turning in his grave in shame" at the accusations from his "countrymen" at Survival International, which has its headquarters in the UK.

I don't usually promote other people's greenwash awards. But this time I make an exception. For this brazen misappropriation of environmental virtue, the NGO Survival, which campaigns for tribal groups, last week gave the company Yaguarete Pora SA its 2010 Greenwash award.

Survival says the uncontacted people are from the Totobiegosode tribe, which is part of a wider family of tribes known as the Ayoreo. "Yaguarete has already destroyed thousands of hectares of the tribe's forests. The company plans to convert around two-thirds of the land to cattle ranching," according to Survival, which has released recent satellite images to prove its claims.

The reclusive forest community has asked for protection via relatives in the wider Totobiegosode tribe, who began legal action on their behalf to secure legal title to their land back in 1993. The case remains unresolved.

The disputed land is 400 kilometres north of the Paraguayan capital Asunción, in the province of Alto Paraguay, where local estimates say 90% of the land is now in the hands of Brazilian cattle ranchers. Media reports say that the government's National Environmental Council last year cancelled logging permits for Yaguarete in the area because of breaches of environmental regulations.

According to documents in support of the reserve plan (pdf) submitted to government authorities, the company has taken over 78,500 hectares, of which it now plans to set aside 27,500 hectares for the nature reserve, of which Survival estimates some 17,000 hectares will be continuous forest.

Plans for the reserve have been drawn up by the National Land Trust, a body set up by a former director of Paraguay's parks department to help landowners create conservation areas. He has won awards for this work, including the Whitley Fund for Nature Award in 2003, which was sponsored by WWF-UK.

But the Survival director, Stephen Corry, says "the nature reserve is textbook greenwashing. Bulldoze the forest and then preserve a bit for PR purposes." Survival is supporting action by a local Paraguayan NGO called GAT to reclaim the tribal lands.

Yaguarete Pora's director, Marcelo Bastos Ferraz, did not respond to questions from the Guardian this week. But the company did issue a statement after receiving the Survival award last week.

"The company decided to establish a wild protected area under private ownership, guaranteeing hunting and fishing rights for hundreds of indigenous families who live in the area," it said. "The Ayoreo-Totobiegosode will be able to use the reserve, and can freely practice their culture and customs."

Fine, but that's not what the Totobiegosode people want, says David Hill of Survival. "They have a long-running law suit claiming legal title to that land themselves."

The company also says it is investing in Paraguay, providing jobs and respecting environmental laws It accuses Survival of "xenophobia", of "profiting by lying" and of "using satire and adopting a Chaplinesque attitude, as well as trying to influence the president of a sovereign country." It points out that there is an international treaty "which guarantees that Paraguay will protect Brazilian investments" in the country. Quite so.

In recent months, the Brazilian government has promised the world it will end the destruction of Amazon rainforest to create new cattle pastures. The tragedy is that it looks as if the reclusive inhabitants of its neighbours' forests are now in the front line.