By Charlotte Beugge

Britain's already hard-pressed householders will be reeling from the news that their water bills are to rise by on average 5.7% from the next financial year - above the rate of inflation.

Water industry regulator Ofwat says that from 6 April, the average water and sewerage bill in England and Wales will go up by around £20 to £376.

The biggest increase will be suffered by the customers of Southern Water who will be hit by an 8.2% rise of £31 a year. But customers of Dwr Cymru, the Welsh water company, will see their bills rise by 3.8% or £16 - perhaps reflecting the increased precipitation in the principality.

According to the BBC, those companies providing water only (sewerage coming from a separate company), those with Bristol Water face a rise of 8.8% or £15 to £181.But Veolia Southeast customers face a 3.3% - or £6 to £188.

As well as inflation, the rises are partly to help pay for infrastructure improvements.

Regina Finn, chief executive of Ofwat, said: "Inflation feeds through into water bills, and this is driving these rises. We will make sure customers get value for money.

"Companies are investing £22 billion by 2015 - more than £935 for every property in England and Wales. This will deliver benefits to us all - from continuing to improve reliability of supplies to cleaner rivers and beaches."

She added that if companies don't deliver on these promises, Ofwat "will take action".

Unlike for electricity and gas, there is no competition for water supply and you have to have your local supplier. There are 20 water companies in England and Wales, some of which are owned by foreign companies.