Raja Azlan Shah FJ:

The respondents ("the Board") had contracted to supply electricity to the appellants. By mistake, it had considerably undercharged the appellants to the amount of $84,624.01 and successfully claimed that amount from them. The learned trial Judge held that the Board was not estopped from claiming that amount although the appellants had utilised the accounts rendered by the Board for the purpose of costing their products. To have admitted the estoppel, so the learned Judge held, would have had the effect of nullifying the statutory provisions of the Electricity Act, 1949 (Revised - 1973).

This is an appeal against that decision.

Before stating the facts on which this appeal turns, and the contentions of Counsel, it seems to be convenient to refer to the relevant statutory provisions of the Electricity Act, 1949 (Revised - 1973) and the Electricity (Board Supplies) Rules, 1949, (LN 515/49; amended LN 235/64).

The Board is a corporate body constituted under s. 3 of the Act, and is accordingly under a statutory duty to secure the supply of energy at reasonable prices (s. 15), to enter into contracts with any person upon such terms and conditions as it may determine (s. 16) and to fix the prices to be charged which shall be in accordance with such tariffs as may, from time to time, be fixed by regulations made under s. 89 (s. 21(1). The Board is under the control and supervision of the Minister who appoints the members (s. 5) and is required to make annual reports and returns and a copy thereof to be transmitted to the Minister as well as to be laid before the Dewan Raayat - (ss. 25, 27). Although the Board has a free hand to enter into contracts for the supply of energy, the rates which it can make and exact are strictly limited, and must be in exact accordance with the provisions of the First Schedule - "contracts at scheduled rates" (r. 29). It has power to amend the schedules and to make charges for energy supplied in different places or districts on different systems, or while maintaining the same system, at different rates (r. 4(5), but that power cannot override the statutory duty of the Board not to show undue preference or undue discrimination as between consumers similarly situated (s. 21(2). Monthly bills are rendered by the Board to the consumer which must be paid within seven days of presentation, failing which the installation may be disconnected without further notice (r. 8(1).

The appellants during the material times carried on a textile business in Butterworth, Province Wellesley. They had entered into a contract with the Board to buy from it electricity energy at Scheduled rates - at Tariff E - Fixed

Block Industrial Tariff. Because at that time a two-way summation system was not available and because of the urgency of the appellants' need, a three-way summation system was installed. Since the factory is using two power transformers, a multiplication factor of 3/2 is required to ascertain the actual units consumed. If a two-way summation metering system is used, then a multiplication scale is not required, and a direct reading would show the actual units consumed. Due to an error of the Board's servants, the correct multiplication factor was not applied, thus the appellants were not rendered proper bills from the commencement of the contract i.e. 16 December 1970, until the omission was discovered on 29 April 1972. At that time an engineer of the Board was taking stock of summation current transformers in order to assess its requirements for the next annual period and he called in these forms as well as the requisitions. It was then discovered that there was discrepancy between Form LLN 98 and the particular requisition form. The former, which is normally used to advise meter readers as to what factor to use on the meter reading, showed a two-day summation metering system, whereas the latter showed a three-way system. Of course, the former is not correct. A junior technical assista