The Government are aware that in some circumstances the use of biodiesel blends can be associated with bacterial contamination in fuel tanks. The problem tends to arise particularly where the biodiesel does not meet the relevant fuel quality standards. The issue is not a new one: biodiesel blends have been used for many years by bus operators in the UK and other countries. It can generally be addressed through good housekeeping practices, such as regular tank cleaning, and by the use of various fuel additives. These are matters for the transport fuel industry to resolve: commercial bus operators and others should ensure that fuel quality requirements are covered in any fuel supply contracts.