A water watchdog has launched an enforcement case against a provider to investigate whether it has failed to develop and maintain an efficient supply system.

Ofwat says South East Water is the worst performer for supply interruptions in England and Wales where there was an average of more than three hours lost per property.

The regulator has categorised the firm as “lagging behind” in a new report and required it to publish a service commitment plan by the end of November to address several areas of underperformance, including supply interruptions.

This announcement follows the watchdog calling in the Board of South East Water before Ofwat’s chair and chief executive to explain its performance over the last 18 months.

South East Water is the current worst performer for water supply interruptions in England and Wales.

In 2022/23 there was an average of three hours, two minutes and 21 seconds lost per property compared with its performance commitment level of five minutes and 45 seconds.

David Black, Ofwat CEO said: “Providing reliable water supplies is at the heart of a water company’s responsibilities.

“Too many customers have been failed too often by South East Water. That is why we are now carrying out a thorough investigation into the company and its service to customers.

“We are clear that water companies must do more to regain public trust and it must start with better service.

“Where this does not happen, we will use all of our powers to ensure the sector delivers better value for both customers and the environment.”

Opening an investigation does not imply that Ofwat will conclude there has been a breach or the regulator will pursue formal enforcement action or impose a financial penalty.

To protect the integrity of the process, Ofwat will not be able to discuss the specifics of the case until the investigation has concluded.

Mike Keil, chief executive of the Consumer Council for Water, said: “Customers’ trust and confidence in South East Water has been undermined by the company’s repeated poor handling of supply interruptions and we will do all we can to support Ofwat’s investigation.

“There was considerable anger and frustration among many people who felt unsupported, compounded by the company’s poor communication.

“Customers have a right to expect better from an essential service provider.”

South East Water says it acknowledges the decision by Ofwat to open the investigation.

“Resilience forms a major focus for South East Water both now, and as a significant part of our PR24 business plan which has been submitted to Ofwat,” a spokesman said.

“We intend to fully cooperate with Ofwat on this matter.”

A PR24 holds water companies to account for the outcomes customers pay for and incentivises companies to go further where it is in the interests of customers and the environment.