SOUTHERN Water has apologised to scores of customers in Hampshire after a data breach saw details, including national insurance numbers, dates of birth, sort codes and bank account numbers, stolen.

Letters and emails have arrived at customers' homes in the last couple of days, explaining what happened and what they should do now.

On January 22, an organisation on the dark web, which is an area of the internet used by criminals, claimed to have obtained data from the utility provider.

The company raised the alarm on February 13 and apologised.

In recent correspondence, it said it had previously detected suspicious activity.

An investigation has been launched, along with the National Cyber Security Centre, as well as other preventive measures.

Water supplies were not affected, said the provider.

Southern Water said it did not know how many customers have been impacted, but estimated it was between five to 10 per cent.

It has assured customers that a link to Experian Identity Plus, offered in the most recent letters and emails, in a bid to help Islanders monitor potential suspicious activity, is safe to use.

It gives 12 months Experian cover for free, as long as membership is activated within two months of getting the correspondence.

Southern Water said it was monitoring the situation and invited customers with questions to contact it, on 0330 303 0025.

Earlier this month, Southern Water said: "Based on our forensic investigations, which are ongoing, we are planning to notify in the order of five to ten per cent of our customer base to let them know that their personal data has been impacted.

“We are also notifying all of our current employees and some former employees.

“We take data protection and information security very seriously and, in accordance with our regulatory obligations, we are making contact with anyone whose personal data may be at risk."

The Information Commissioner's Office (ICO) also confirmed it had received a report about the incident and was investigating.