These will ensure developers are paid a minimum electricity tariff for several decades to recoup the high upfront building costs.

The change means one million customers on the standard variable electricity tariff will fork out an extra 42 a year.

Customers who pay on receipt of a quarterly bill will find that their gas prices will fall by only 5 per cent, with no change in the electricity tariff.

In that same year, the electricity tariff was set for all companies at a level below their actual costs.

However, the electricity tariff decreased by 6%.