Shell and BP have been  warned by investors that their involvement in unconventional energy production  such as Canada's oil sands could turn out to be the industry's equivalent of the  sub-prime lending that poisoned the banking sector and triggered the current  financial crisis.
 "The recent banking crisis has shown how the financial markets can  totally misjudge both the risks and values inherent in company balance  sheets," he said. "Oil companies depend on oil reserves for  their market values. BP and Shell are two of our most trusted stocks, but it is  a shocking fact that 30% of Shell's oil reserves are in tar  sands.
 "This report unveils how dangerous this  approach is. There is a good chance that tar sands could be to the oil industry  what sub-prime lending was to the banking  sector."