Jan.12, 2010, 7:00AM GMT

Officials suspect that the traders have been avoiding VAT payments on carbon permits – which must be bought by heavy industry to cover the cost of their emissions.

They believe that permits have fallen prey to carousel fraud, where goods are imported tax-free from other countries then sold to one or more buyers without charging the tax. The trader then disappears, pocketing the VAT.

The British traders were allegedly operating from Tournai, in Belgium, to take advantage of the country's 21pc VAT on carbon permits.

They deny the authorities' claims that they were buying permits in Britain, and selling them on to banks via intermediaries without paying tax.

The charges come several weeks after Europol, the Europe-wide police force, warned that the total market for fraudulent purchase of credits may have been worth €5bn.