Southern Water has seen complaints rise by more than 50 percent in the past year, new figures reveal.

Nationally complaints about water companies to the official customer watchdog are at their highest level since 1994.

High charges and problems with bills are the greatest source of gripes across all firms.

Customers in England and Wales lodged 13,603 complaints with the Consumer Council for Water in the 12 months to March 31 - up 10% on the previous year.

A surge in complaints to four water companies - mainly about billing glitches - was behind the overall annual complaints increase.

These companies are: Severn Trent Water, South East Water, Southern Water and United Utilities.

Complaints about other water and sewerage firms in England and Wales remained stable or fell slightly.

Nearly half (49%) of all complaints made to CCWater were about either billing or charges.

Complaints against Southern Water in the year to March 31 increased by 52% to 777.

CCWater chair Dame Yve Buckland said it was ''disappointing'' that billing systems were causing so many problems. Some customers had even been unable to reach their supplier's staff by phone to complain.

CCWater, formerly Water Voice, is the statutory water consumer body which represents customers in England and Wales.