A recent investigation has uncovered widespread failings in the new markets for greenhouse gases, suggesting some organisations are paying for emissions reductions that do not take place. Others are meanwhile making big profits from carbon trading for very small expenditure and in some cases for clean-ups that they would have made anyway.

The growing political salience of environmental politics has sparked a 'green gold rush', which has seen a dramatic expansion in the number of businesses offering both companies and individuals the chance to go 'carbon neutral', offsetting their own energy use by buying carbon credits that cancel out their contribution to global warming.

The burgeoning regulated market for carbon credits is expected to more than double in size to about $68.2bn by 2010, with the unregulated voluntary sector rising to $4bn in the same period.

The investigation found:

1) Widespread instances of people and organisations buying worthless credits that do not yield any reductions in carbon emissions.

2) Industrial companies profiting from doing very little - or from gaining carbon credits on the basis of efficiency gains from which they have already benefited substantially.

3) Brokers providing services of questionable or no value.

4) A shortage of verification, making it difficult for buyers to assess the true value of carbon credits.

5) Companies and individuals being charged over the odds for the private purchase of European Union carbon permits that have plummeted in value because they do not result in emissions cuts.

Some companies are benefiting by asking 'green' consumers to pay them for cleaning up their own pollution. For instance, DuPont, the chemicals company, invites consumers to pay $4 to eliminate a tonne of carbon dioxide from its plant in Kentucky that produces a potent greenhouse gas called HFC-23. But the equipment required to reduce such gases is relatively cheap.

The investigation has also found examples of companies setting up as carbon offsetters without appearing to have a clear idea of how the markets operate. One offsetting company invites consumers to offset carbon emissions by investing in enhanced oil recovery, which pumps carbon dioxide into depleted oil wells to bring up the remaining oil. However, the company said that because of the high price of oil, this process was often profitable in itself, meaning operators were making extra revenues from selling 'carbon credits' for burying the carbon.

There is nothing illegal in these practices. However, some companies that are offsetting their emissions have avoided such projects because customers may find them controversial.