SOUTHERN Water has once again been named the worst in its field after failing to provide customers with “timely, complete and accurate” information.

The Worthing-based water company has been ranked bottom by industry regulator Ofwat in an annual review.

The firm was the only water company to be given two serious concerns and was among four of 17 peers nationwide to be given the “prescribed” status.

A Southern Water spokeswoman said the firm was disappointed by the regulator’s decision but said it would work with Ofwat to improve.

South East Water, the other supplier of water in the county, was top of the class and one of only three given the self-assured rating.

Ofwat said it was looking for water companies to meet high standards of assurances, provide clear, transparent and accurate data and demonstrate a successful and positive approach to stakeholder engagement.

The regulator found two serious concerns and four minor concerns with Southern Water's data quality, transparency, board governance and communication to stakeholders.

In dropping the water company down to prescribed, the regulator said Southern Water had exhibited behaviour leading to a reduction in the trust and confidence that stakeholders could place in it.

Of serious concerns was a decision by the firm to change the questions it asked in customer surveys meaning it was now impossible to measure how it was doing against its business plan performance commitments.

The company failed to tell regulators about the change until 18 months later despite a clear warning that water companies had to stick to those agreed with Ofwat.

Southern Water claimed that the original survey questions produced too many "don’t know" responses.

Ofwat also criticised Southern Water for failing to provide “timely, complete and accurate” information in response to three cases they had opened against the water firm since 2015.

A Southern Water spokeswoman said: “While we are disappointed with Ofwat’s decision to move Southern Water into the prescribed category within its company monitoring framework, we will use the ratings assessment to drive further improvements across the company to ensure we are providing information in an open and transparent manner which benefits our customers and stakeholders.

“We look forward to working with Ofwat in making these improvements.

“We changed our survey to provide clearer, more accessible questions. In doing so, we took what we thought were the necessary steps, liaising with Ofwat, an external consultant and our customer advisory panel.”