THAMES Water has announced plans to increase customers’ bills to an average of 91p a day by 2015.

The water firm claims its customers are currently paying “unsustainably low” bills, which for an average household currently works out at about 77p a day.

According to the company’s five-year business plan, the biggest single rise will come next year, when bills go up by 10.5 per cent, with smaller rises in every following year. By 2015, the firm predicts the annual bill for a typical household will have increased from £283 to £331.

A spokesman said the increase was needed for its £5.5bn modernisation of water mains and sewers.

She said: “Decades of underinvestment mean our bills, the UK’s cheapest, are unsustainably low.

“Although bills must rise, we’re keeping them as low as possible, below the forecast industry average, at less than £1 a day by 2015.

“As well as vital upgrades to our network, our proposed investment for the next five years will safeguard 10,000 jobs.

“In 2004, Ofwat was criticised for not being tough enough on water companies, so this time round we’re expecting them to be tougher on us, which ultimately means being tough on our customers.”