Warning: Chief executive of Scottish and Southern Energy Ian Marchant

The UK's second biggest domestic energy supplier yesterday warned that punishing price rises will hit before the winter.

Scottish & Southern Energy (SSE), which has 8.8million customers, said the full impact of soaring oil costs on electricity and gas prices 'has still to be felt'.

Chief executive Ian Marchant said: 'We are continuing to resist the pressure to put up prices for domestic customers, but doing so is becoming more difficult by the day.

'I can't see it won't happen before winter.'

The company told investors that the majority of its profits would be made between October and March - a signal that price rises are on the way.

The price comparison service energyhelpline.com predicted that energy prices could rise by as much as 60 per cent by the end of this winter.

Director Aamir Baloch said: 'The latest round of crippling energy price rises is imminent.

'Consumers should brace themselves for the biggest rises in UK history.

'Whoever goes first will cause a domino effect.

'We predict they will raise their prices by 20 per cent in the next couple of weeks.

'We expect two rounds of price hikes by the end of the winter, raising an average bill by 60 per cent in total.'

SSE is one of the 'big six' UK power suppliers. They have been accused of failing to ensure that millions who are in fuel poverty - spending more than 10 per cent of their disposable income on heat and light - are being offered cheap social tariffs.

A report published today by the industry regulator Ofgem highlights the fact that some of these social tariffs are not the cheapest deals available.