The editor of Which? finds high level of customer satisfaction

Research published in Which? magazine on Thursday finds that the average household can save around £70 a year by changing gas companies.

Since May everyone in England, Scotland and Wales who is on mains gas has been able to choose between more than 20 suppliers.

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So far, around 4m people have already switched companies or signed contracts to do so.

Which? Editor Helen Parker says nearly everyone can save money be switching gas companies.

But the figures are disputed by British Gas, which questions the way they were calculated.

Most people were happy with a change

Which? surveyed about 9,000 people, and found most people who had changed were happy with their new gas companies.

However, Ms Parker says savings can also be made without changing companies.

"You could simply change the way you pay, and save £50 a year with British Gas, for example, by paying by direct debit," she said.

Although most people surveyed said changing companies had been easy, one in five thought their new supplier was worse than British Gas for meter reading.

A few people also reported administrative delays.