According to environmental officials, the gang was responsible for illegally chopping down timber worth more than £200 million during 14 years, most of it in the past two years.

The area of forest cleared by the gang is estimated to be the equivalent of 52,000 football pitches.

Among those to have been arrested was Moacir Pires, the environment minister of Mato Grosso state. He was dismissed yesterday by Blairo Maggi, the Governor of Mato Grosso, whose administration is, according to environmentalists, a key supporter of efforts to clear the state’s remaining forests.

Senhor Maggi is known as “the king of soy” and is the world’s biggest soy businessman.

Others to have been detained included the directors of several logging companies, senior local government officials and agents from the federal body charged with protecting the rainforest.

Police said that the gang consisted of “loggers and specialists in the illegal extraction and transport of timber who corrupted public officials”.

Investigators say that the gang operated in Indian reservations and national parks, where the loggers bribed officials to allow them into restricted areas and to provide them with falsified documentation to ease the transport of the timber to other areas of Brazil and abroad.

So far more than 80 arrests have been made across six of the country’s Amazonian states. Forty-seven of those detained are officials at Ibama, the main federal body in Brazil’s fight to protect the world’s biggest rainforest. Dozens of other suspects are still being sought.

The arrests centred on Mato Grosso, where half of all forest destruction in Brazil took place in 2004, the second worst year of deforestation on record. Two thirds of forest clearing in the state last year was illegal.

Four logging companies in the state were closed down as part of the investigation. The federal authorities have ordered a virtual halt to all logging operations in Mato Grosso while investigations continue.

All transport of timber has been halted for 30 days and all logging companies will be inspected in the next 60 days.

Among the 47 officials arrested was the state director of Ibama in Mato Grosso, who is accused of illegally earning £100,000 over the past two years for his role in the scheme.

Police showed off bundles of falsified documents that they say were drawn up by corrupt officials to pass off timber that had been illegally felled as legitimate.

Police say it would have required the gang to make 66,000 trips by lorry to ferry all the trees they felled out of the jungle.

The Government says that the investigation shows its commitment to protecting the rainforest and promised that there would be no hiding place for officials who connived with groups they were supposed to be policing.

“We are going to cut the flesh to take out this tumour of corruption,” said Marina Silva, the country’s Environment Minister, at a conference announcing details of Operation Curupira, named after the figure in Brazilian folklore whose role is to protect the forest.

Environmental groups had accused the Government of turning a blind eye to the problem so as not to upset Brazil’s rapidly expanding agri-business sector, which is an important source of the foreign currency needed to pay off the country’s huge debt. Typically loggers are the first group to strip an area of cleared forest, followed by ranchers and soy farmers.

President da Silva promised reform last month after the publication of government statistics showing that Brazil lost 26,130 sq km (10,088 sq miles) of rainforest between August 2003 and August 2004.

The Government now says that 20 per cent of the original forest has gone. The destruction takes place in remote states, far from most central government control.

As in the case of the gang broken up this week, campaigners say that the main threat comes from loggers working with corrupt local officials and environmental protection officers who strip out lands often nominally under protection.

As well as the environment, victims include the Amazon’s indigenous peoples who are hunted out of their traditional lands by loggers and ranchers.

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