Mr. Opik: To ask the Chancellor of the Exchequer if he will assess the advantages of reducing the duty on liquid propane gas.[50480]Mrs. Liddell: The environmental benefits of gas as a road fuel are well known and this has been reflected in the fact that the dutyon road fuel gases (liquefied petroleum gas (propane) and liquefied natural gas (methane)) has been frozen for the second Budget insuccession. This has increased the differential in favour of road fuel gases in recognition of their environmental benefit and morethan fulfilled the pledge to maintain the duty differential with more conventional fuels for the lifetime of this Parliament.