SCOTTISH Gas staff have been described as ''thugs'' by a power watchdog for breaking into a house and replacing an electricity meter even though the family was not its customer.

A spokesman said it was the worst case of its kind ever brought to energywatch.

Andrew McKay, the home owner, said it happened at the end of a long-running dispute with the company.

Mr McKay, 39, of Livingston, West Lothian, had a call last August from a salesman who convinced him to switch his gas and electricity supply from Npower. After signing up with Scottish Gas, Mr McKay, a father of three, said he had a change of heart and decided to continue getting his electricity from Npower.

He said he told Scottish Gas, and thought no more about it until he received an electricity bill from the company.

Despite numerous telephone calls and a letter explaining that he was not a Scottish Gas electricity customer, Mr McKay, a mature student, said the bills continued.

''I was in the middle of my exams and decided I was too busy, so I just ignored the bills,'' he said. ''They started to send people to my door. I had about four visits, and each time I told them I was with Npower.''

Matters came to a head in May this year when his wife, Denise, arrived home and found the back door open.

''They had broken the lock to get in and had taken out the credit meter and replaced it with a prepayment meter,'' he said. ''We had to go down the shops to get payment cards even though we weren't with Scottish Gas.''

The company has accepted that the family were not its electricity customers and has offered a (pounds) 130 refund and (pounds) 250 compensation.

Mr McKay has rejected the compensation offer. ''We felt violated. You can't have people breaking into your house just like that.''

Allan Asher, from energywatch, said: ''This appalling violation of consumer privacy is the worst case of its kind ever brought to energywatch. Mr McKay repeatedly proved that Scottish Gas did not supply him with electricity, yet they ignored him and persisted in obtaining a warrant. Then they broke into his home and behaved like thugs.''

Scottish Gas said it was ''extremely sorry for the problems that Mr McKay has experienced'' and admitted ''errors were made''.

Clare Welsh, for Scottish Gas, said: ''With regard to disconnections, as energywatch knows, this process is strictly regulated. We would stress that this is always a measure of last resort.'' She said it involves a recorded delivery letter, which ''clearly sets out the disconnection process. This letter is signed for by the customer.''