South West Water (SWW) customers will be able to opt out of a controversial water tariff trial after initially being told it would not be possible.

Under the two-year scheme, introduced in October, the firm announced that 3,500 customers with water meters would be charged less during the winter months - between October and March - but three times more during the summer.

But the move sparked an angry response from some customers who pointed out that they had not been given a choice as to whether they wanted to be included in the trial, prompting SWW’s U-turn.

The announcement follows parent company Pennon Group’s half-year results, showing a loss of £38.8m, partly due to £16.3m from costs incurred by this summer’s cryptosporidium outbreak.

In the half-year declaration, SWW’s CEO, Susan Davy, said in reference to the incident: “When things go wrong, as they did for customers and businesses in and around Brixham earlier this year, we put it right, with no excuses. But we know we have more to do.”

Ms Davy, who earlier this year accepted a 58 per cent pay rise, taking her annual salary to £860,000, also said customers across the South West “found their bills affordable for the first time”.

The tap water poisoning incident impacted on some 17,000 households in the Kingswear, Hillhead and Brixham areas after a parasite got into the supply in May.

There was a boil notice lasting from May 15 to July 8 as dozens of people fell ill with cryptosporidiosis, causing diarrhoea-like symptoms.

The £16.3m hit was due to having to compensate customers, as well as providing bottled water over an eight-week period and carrying out work to clean and filter the network.

The incident is currently being investigated by the Drinking Water Inspectorate (DWI).