UK utility South East Water Ltd. is failing to provide reliable supplies to customers, prompting the regulator to start a probe to find out why.

South East Water has already been categorized as “lagging behind” in the latest Water Company Performance Report and its chief executive officer has been called in to defend poor operations to Ofwat, the regulator said in a statement Thursday.

“Providing reliable water supplies is at the heart of a water company’s responsibilities,” said Ofwat CEO David Black. “Too many customers have been failed too often by South East Water.”

Ofwat is under pressure to hold companies to account for failures after a sewage crisis that has enraged many customers. Water companies need to increase bills to pay for future investment in the network at a time when public confidence in their integrity is very low.

South East Water is currently the worst performer for water supply interruptions in England and Wales. In 2022-23, there was an average 3 hours, 2 minutes and 21 seconds lost per property, below its performance commitment level.