by Martin Jefferies

Households in Kent will be paying as much as £30 a year more for their water from April 1.

Ofwat, which regulates the water and sewerage industry, announced today that bills would rise by an average of 5.7% to £376.

But Southern Water customers will pay, on average, £416 a year – a rise of 8.2%.

Thames Water bills will also rise by more than the national average – up by approximately 6.7% (£21) to £339.

Households whose water is supplied by South East Water will pay the company an average of 4.6% more in 2012/13. Their sewerage charge, which is billed separately, will also rise.

Regina Finn, chief executive officer at Ofwat, said: "We've listened to customers. They told us they wanted bills kept down, while maintaining safe, reliable water supplies. We challenged companies hard to deliver this.

"We understand that any bill rise is unwelcome, particularly in tough economic times. Inflation feeds through into water bills and this is driving these rises."

Across the country, water companies are spending £22bn on improving sewage treatment works and replacing water mains.

South East Water is set to spend nearly £60m on projects including a new reservoir in Aylesford, which will increase the amount of water the company can store to 10m litres.

Paul Butler, managing director, said: "We appreciate that some of our customers may be experiencing financial difficulties and we have measures in place to help those customers facing real hardship."

Meanwhile, Southern Water will invest £1.8bn, with improvements including an upgrade to its treatment works at Lydd.

Matthew Wright, the company's chief executive, said: "By ensuring investment in our communities we are able to support thousands of jobs, while delivering improved services and a wide range of environmental improvements, such as cleaner seas and rivers."

Martin Baggs, chief executive of Thames Water, added: "We're continuing to deliver our £1bn-a-year programme of must-do infrastructure investment, as well as continuing to urge everyone to use water wisely ahead of a likely summer drought."