asked the Minister of Power the total electrical generating capacity of the Central Electricity Generating Board in June, 1964; how this compares with June, 1958; and what additional capacity is now under contract or construction.

Total capacity in June, 1964, was 33,151 megawatts sent out and this was 10,553 megawatts greater than in June, 1958. An additional 28,990 megawatts of capacity is now under contract or construction.

In welcoming the advance which these figures reveal, may I ask my hon. Friend what margin of capacity will be available in the coming winter as compared with last year? Will he indicate also the amount of spare capacity of oil-fired stations in the United Kingdom at the present time?

The gross margins of plant in average cold spell weather are now slightly better. These figures, I must tell my hon. Friend, do not allow for plant out of commission. In 1963–64, the margin was 8·8 per cent. In 1964–65, it will be 9 per cent.

Would not my hon. Friend agree that the increase in the oil-burning power stations adds a hazard to health by the increased discharge of sulphur dioxide in the air, which in conditions of fog affects both human lungs and buildings? Is anything being done to deal with this health hazard?

Considerable research goes into this matter, on which, I believe I am right in saying, even medical opinion is divided. I remind my hon. Friend, however, that before consent is given to the construction of any power station, my right hon. Friend has to be satisfied that there is no risk to health.