Energy consumers will be automatically compensated up to £120 if they are mistakenly switched to another supplier and not promptly returned, under new Ofgem rules.
Industry regulator Ofgem said the company offered tariffs to 8,815 customers when visiting a bespoke page on price comparison website Utility Discount, which was accessible only via an online advert.
Sudden severe weather earlier this year, which caused water supply outages across the UK, has prompted Ofwat to review the compensation provided to customers.
Bristol Water has paid out more than £100,000 in compensation to customers who experienced supply interruptions after the discovery of cryptosporidium at its Clevedon treatment works in January.
Ofwat has been asked to report to the government by the end of the month with “initial lessons” about water supply disruptions throughout the country following the cold spell and rapid thaw.