Ms Wynne was threatened with legal action

Jean Wynne, from Wrexham, was told that police might be called to help recover the money she was said to have owed.

Ms Wynne got her first bill in June, demanding she paid £20.76, followed by two reminders and a final demand.

Despite writing back to say she only used electricity and oil-fired central heating, she was then warned that legal steps could be taken.

"We have the letter telling us they are going to get a court order and the man will be accompanied by a policeman to collect the £20.76," she said.

Energywatch's Jocelyn Kernick said they had to deal with several mix-ups

"My bills are always paid on time and I wouldn't do that."

On Thursday, British Gas told BBC Wales there had been a mix-up and an apology for the inconvenience was in the pipeline.

A spokeswoman for energy services watchdog Energywatch said they had dealt with several similar cases.

"We do get lots of cases where there have been address mix-ups, perhaps where somebody has been disconnected at the wrong address," said Jocelyn Kernick.

"Or maybe where they have had their supply transferred erroneously where they didn't want it to be."