Customer complaints against water companies in England and Wales have risen by 11 per cent over the last financial year, the industry's watchdog has revealed.
The Consumer Council for Water (CCWater) claimed that customer trust was becoming "stretched" following the "significant" rise in complaints.
The consumer body, which replaced the independent watchdog Water Voice in October, said that along with its predecessor, it had received 12,359 complaints in the 2005/06 financial year.
The most common complaint cited by customers related to un-metered bills, with 66 per cent more consumers protesting about them compared to the previous year. Complaints about metered bills were up 40 per cent.
Delays in connecting customers to mains supplies were also a bugbear for water users, with complaints up by 35 per cent.
Severn Trent Water was the company to attract the biggest overall increase in complaints. CCWater received 1,164 complaints about the firm in the six months to March 31st, a 54 per cent rise on the previous year.
Meanwhile, United Utilities also saw a large increase in customer grievances, attracting 1,138 complaints over the same period, representing a 41 per cent increase on the previous year.
The utilities firm, which supplies water to consumers in the north-west, told the BBC that the rise in consumer complaints about its business had occurred because of "teething troubles" with a new billing system.
Although customers made 4.5 per cent fewer complaints about other water companies during the six month period, CCWater said that the overall increase in consumer objections was of concern.
"From our research we know that consumer trust is getting stretched," said the chairman of CCWater Dame, Yve Buckland.
"They expect to see service improvements and reliable supply alongside returns to shareholders," she added.