Are plastic bags actually greener than paper?

So please raise an eyebrow with me to a stimulating article in the Independent newspaper. It reveals the existence of a report, commissioned by the U.K. government, that concludes that plastic bags are actually less harmful to the environment than either paper or cotton versions.

I know that doesn’t sound right, does it? I live the merest gust of wind away from San Francisco, where plastic bags are banned. I have always been told that paper is green, recyclable, and the finest way we can make use of the Amazon forest.

So how could it be that high-density polythene is actually greener?

Source: Cnet.