Here
Yes it's the Daily Fail, but according to the article the green credentials of washable nappies were discounted by the Environment Agency in 2007.
Apparently there is "no significant difference between the environmental impacts of disposable, home use reusable and commercial laundry systems."
I'll be honest - it's always puzzled me how washable nappies could be considered to be friendlier to the environment because of the use of washing machines and chemicals to clean them.