Southern Water received the highest number of customer complaints across the country for the fourth straight year, according to a report by an industry watchdog.

The company, which provides water and sewage across the majority of Kent, had a 10% increase in written grievances over the last year, said the Consumer Council for Water.

It received more than 77 complaints per 10,000 connections, more than twice the industry average.

It is among four firms which have been asked to report back to the watchdog by the end of October explaining what steps they have taken or are planning to take to drive down complaints.

Another of these is Affinity Water, which covers the Shepway and Dover regions. It was the worst performing water-only company with an 82.3% jump to more than 36 complaints per 10,000 connections.

Overall, 10 of the 21 water companies in England and Wales saw an increase from 2015-16.

However, the total number of complaints fell for the eighth straight year – down 0.5% to 106,196 – with South East Water, which covers large areas of the county, reporting the largest reduction of 38.2%.

Tony Smith, chief executive of the Consumer Council for Water, said: “What is particularly alarming is the very substantial increase in complaints some companies have reported.

“We can’t allow the good progress that has been made by the industry in recent years to be reversed.”

Southern Water said billing complaints had pushed it into the bottom spot but said the number of people who took issue with its water services was among the lowest in the industry.

“We accept there is still much more for us to do to come in line with the rest of the industry and we are continuing to work with CCW to drive forward further improvements..." - Simon Oates, Southern Water

Director Simon Oates said: “We accept there is still much more for us to do to come in line with the rest of the industry and we are continuing to work with CCW to drive forward further improvements.

“We want to reassure our customers we remain fully committed to continuing the improvements we have already made, and bringing our performance up to the standard they quite rightly expect from us.”

Affinity Water customer relations director Amanda Reynolds said: the firm had created a customer experience improvement programme in July last year after consulting with 70,000 customers.

She said: “This is making a real difference and in the second half of the year, we saw a 35% decrease in complaints compared to the first half of the year.

“I am pleased to see that this improved trend is continuing and that we are heading in the right direction.

“I am determined to continually improve our service levels and achieve great results for our customers.”

Steve George, customer services director at South East Water, Kent's best performing company, said: “We are constantly listening to customers and using their feedback to improve our services.

“New for this year is our MyAccount online service, where customers can manager their water accounts, and view, download or print their bills at any time of the day or night."