asked the Secretary of State for Energy, further to his reply dated 14 February concerning petroleum product prices, whether he will circulate in the Official Report a statement showing the reason for the 2,628 per cent. increase in the refinery margin on naphtha between 1973 and the third quarter of 1979; and what effect this increase has had on the cost of making continuous polyester fibre yarns of the kind imported from the United States of America.

It is not valid to say that the refinery margin on naphtha in the third quarter of 1979 is 2,628 per cent. of its value in 1973, since naphtha can only be produced from crude oil jointly with a range of other products, and thus the refinery margins can only be computed for a typical mix of products obtained from the barrel of crude oil. The pricing of oil products in the United Kingdom is largely determined by world markets, and the increases since 1973 reflect the upsurge in world crude oil prices. It is estimated that the increase in the price of naphtha since January 1977 may have added about £150 a ton to the cost of continuous polyester filament yarns.