Southern Water has revealed the cause of a water supply failure affecting 15,000 households across Southampton and Winchester.

Thousands of people have been left with little to no running water after supply was cut off almost 24 hours ago.

Three bottled water stations have been opened so far to help families in the area.

Southern Water initially said the problem was down to a "failure" at its Otterbourne works.

However, the firm has now released more details on the issue.

READ MORE: Live updates as taps run dry for second time in weeks

A spokesperson said: "During planned maintenance at our Otterbourne water supply works, our systems detected that untreated water was not being filtered correctly.

"Our systems are designed to automatically shut down to avoid any risk to our water supplies should this situation arise.

"Work has been under way since yesterday evening to safely contain, drain, clean, disinfect and refill the part of the system affected.

Daily Echo: The bottled water station at Cantell SchoolThe bottled water station at Cantell School (Image: Newsquest.)

"Once the system is refilled, we will undertake extensive water quality testing before putting water back into supply.

"We would never take risks on the quality of the water that we provide and it’s important that we carry out this process in the correct way. This is why it's taking time."

The firm has been widely criticised by councillors and MPs today for its recent poor performance.

The latest supply failure comes after thousands of residents were left without water just days before Christmas.

The company says it will take 48 hours for supply to be restored.

Vulnerable customers have been urged to call 0330 303 0368 to have bottled water delivered to their homes.