Wholesale gas prices for this winter are the highest in the world and are set to rise further, increasing the likelihood that British energy groups will be forced to increase bills further.

Wholesale gas to be delivered in January is trading at more than 80p per therm, which is about 25 per cent higher than prices on the Continent and in the US and a quarter above prices in the UK for the same period this year.

Although new gas pipelines from Norway and Holland, due to become operational this winter, will ease the pressure on prices, many analysts fear the new supplies will arrive too late to make a significant difference this winter.

"Until these projects are delivered, there is a lot of anxiety premium in forward wholesale gas prices,'' said Jeremy Nicholson, the director of the Energy Intensive Users Group.

The shortfall has been accentuated by falling gas deliveries from the North Sea and the failure of the interconnector - an existing gas pipeline between Belgium and the UK - to transmit gas at maximum capacity throughout last winter.

Last week British Gas, owned by Centrica, said it was increasing gas prices from September by 12.4 per cent and electricity prices by 9.4 per cent. This is the second rise from the UK's largest gas supplier this year.

Some 180 businesses in the West End of London were hit by power cuts on Thursday and Friday, costing them an estimated pounds 20m in lost sales. EDF Energy, the supplier in the area, said high temperatures had increased demand, putting pressure on the network.

Last night Ken Livingstone, the Mayor of London, expressed anger at the cuts. "The present situation must be resolved as rapidly as possible in the interests of customers and to stop the losses being suffered by West End businesses,'' he said.