British Gas says it is experiencing a 'difficult year'

British Gas owner Centrica first announced the rises in July, with gas bills up by 12.4% and electricity bills rising 9.4%.

The firm has blamed the move, its second set of price rises this year, on continuing high wholesale energy costs.

Consumer groups and analysts warned that UK prices may still have to rise.

Difficult outlook

As well as British Gas, most of the UK's other largest suppliers also have increased their prices, citing near record oil prices and supply problems that have pushed up wholesale costs.

On Monday, British Gas said it would not increase prices again this year - although it said that its decisions in 2007 would depend on international market conditions.

Among its rivals:

• Scottish & Southern said that it had promised not to hike prices in 2006
• Electricite de France said it had no plans "at the current time" to lift costs
• NPower said it could neither rule in nor rule out an increase in costs.

The companies said pressure on prices may ease in coming months as more gas supplies and storage facilities become available, and this year's winter is not expected to be very cold.

However, consumer groups and analysts said that despite the reassurances from suppliers, there was every liklihood that firms would have to start annoucing future price increases before the end of this year.

According to watchdog Energywatch, the 4 September price hike means British Gas is now the most expensive energy firm in the UK.

The company's average annual gas bills had increased by 91% since 2003, while its electricity bills had risen 81% over the same period, Energywatch said.

Global factors

The latest price rises at British Gas come after it reported record losses of �143m for the first six months of this year.

We expect suppliers to do more to... reduce the burden on the poorest who are often paying the most Allan Asher, Energywatch Poor 'penalised' by energy firms

It last increased costs for its 16.5 million customers by 22% in March.

Energywatch, along with charities Help the Aged and Child Action Poverty Group, warned that old people as well as the disabled are set to be the most affected by the higher gas and electricity prices.

As frequent users of prepaid meters, they are being charged even more than those billed on a quarterly basis, the organisations said.

Meter customers are being charged as much as �173 more for their gas, and their electricity bills are as much as �113 higher annually, the groups claimed.

The coalition is calling on the six largest energy companies, including British Gas, to set the rates for prepaid meters at the same level as those for consumers who are sent quarterly bills.

The price of wholesale gas in the UK have been increasing as the country's stocks in the North Sea have declined, forcing more to be imported from Europe.