A new British study suggesting that disposable and cloth diapers have the same impact on the environment has some environmental groups seeing red.

The Environment Agency released a report Thursday comparing the two types of diapers, measuring everything from the impact of the raw materials used to make them to the effect of transporting, disposing and laundering them.

While companies that sell disposable diapers say the study shows parents shouldn't feel guilty about using their wares, advocates of cloth diapers say the study is not scientifically valid.

Elizabeth Hartigan of the Women's Environment Network said the sample size for assessing the way parents use cloth diapers was too small and so it was unfair to draw conclusions.

The study is based on surveys from more than 2,000 parents and guardians who used either cloth or disposables.

In an interview with the BBC, Hartigan said parents could lessen their impact on the environment by washing diapers in cold water and using energy efficient washing machines.

Tricia Henton, director of environmental protection at the Environment Agency, a quasi-government organization, told the BBC that getting a big sample of cloth diaper users was difficult as only about five per cent of British parents use them. Henton said her group would carry out further work to verify its study.

According to the agency, parents in Britain bought about 2.5 billion disposable diapers in 2001, accounting for 2.5 per cent of household waste.

The study suggested that the environmental impact of disposable diapers relates to their production and disposal in landfill sites. For cloth diapers, environmental degradation came from generating electricity used in washing and drying.

Henton said she hopes manufacturers of disposable diapers will use the study to improve the environmental performance of their products, and that cloth diaper users will wash them in bigger loads at lower temperatures and hang them to dry.