The integrity of the European Union's embattled Emissions Trading Scheme (ETS) was rocked by revelations in December that carbon-trading tax fraud has cost European taxpayers more than €5 billion.
On December 9, the EU's law enforcement agency Europol estimated up to 90% of all market volume was fraudulent in some countries.
Europol spokesperson Rafael Rondelez told the December 10 EU Observer the intangible nature of carbon credits make them "an incredibly lucrative target for criminals".
"It makes it easier for fraudsters because it's an intangible good", he said. "Before, goods actually had to be transported from one member state to another. You had to prove that goods were really being transported.
"With this, it's just the click of a mouse."
Carbon Trade Watch's Oscar Reyes told the EU Observer the ETS should be abandoned in favour of the direct regulation of polluters.
"While the ETS has so far not resulted in reduced emissions, the European Commission has regularly pointed to the high volume of trading on emissions exchanges as a sign that the market was working", he said.
"Europol has now revealed this to be a sham."
In a November briefing titled "Carbon credit fraud: The white collar crime of the future", accounting firm Deloitte said the Rudd government's proposed Carbon Pollution Reduction Scheme could also be open to fraud.
Deloitte Forensic's Chris Noble: "An emissions trading scheme may well attract highly organised fraudsters from overseas and Australia prepared to exploit arrangements that will be trading in billions of dollars.
"The warning signs are already apparent, with many schemes falling into the traditional rationalisation approaches."
Meanwhile, the independent think tank Open Europe found the EU ETS had delivered millions in dollars in windfall profits to some of Europe's biggest oil, gas and cement companies, due to the over-allocation of free permits.
It also found the two biggest carbon trading exchanges made more than €57 million in transaction fees alone in 2009.
Open Europe's Stephen Booth said: "It is a perverse situation when our chief environmental policy is granting such huge benefits to companies that pose the most harm to the environment.
"Profits should be greasing the wheels of the emissions trading system rather than lining the pockets of the biggest polluters and carbon exchanges."