A watchdog has accused an energy company of penalising its Sussex customers with increased prices.

Energywatch Southern said it was disappointed bills for some Southern Electric customers would go up by nine per cent from July 1.

Southern Electric served customers west of Littlehampton and Arundel before the free market was introduced for electricity supply.

Electricity bills for customers in the old Southern Electric region will rise by only 3.7 per cent, while customers in other parts of Sussex face an 8.8 per cent rise.

The company said it provided electricity to fewer than five per cent of people in Brighton and Hove.

People who started buying gas from Southern Electric from February this year face a four per cent rise.

People who have been buying gas from the company for longer face a nine per cent increase in their bills.

Southern Electric spokesman Denis Kerby said: "We still offer some of the cheapest electricity and gas prices.

"Despite this increase, we are somewhere in the region of six per cent cheaper than the home electricity region (EDF Energy) and four to ten per cent cheaper than British Gas."

He said Southern Electric was the only supplier given a five-star rating by the consumer web site Youswitch.com Southern Electric is an operating company of the larger Scottish and Southern Energy.

However, Jean Shanks, director of Energywatch Southern, said it was a shame Southern Electric had joined the "merry-go-round" of price increases.

She said: "I am particularly concerned customers in Sussex are faced with higher increases than customers elsewhere in the country."

She urged people affected by the price rises to shop around for a cheaper deal.