Household water bills in England and Wales will increase by an average £31 a year over the next five years, regulator Ofwat has announced.

The increase is significantly higher than the expected average rise of around £20 a year per household, outlined in the regulator’s draft proposals in July.

Ofwat said the increase would pay for a £104 billion upgrade of the water sector to deliver “substantial, lasting, improvements for customers and the environment”.

However, despite the average £31 a year increase figure, households will face a heavy average hike of £86 or 20% in the next year, excluding inflation, with smaller percentage increases in each of the next four years.

The average bill will rise by a total of £157 or 36% over the next five years.

Some firms have been allowed significantly higher increases. Southern Water customers will face a 53% increase and Severn Trent households will see their bills rise by 47%, before inflation.

DWr Cymru and Hafren Dyfrdwy have both been allowed to charge 42% more, while Yorkshire Water bills will rise by 41%.

Thames Water is to be allowed to hike consumer bills by 35%, as the regulator also handed it an £18.2 million fine for paying “unjustified” dividends to shareholders.

The ruling falls well short of the 59% Thames Water had said it needed in the run-up to the decision, as the embattled water company tries to negotiate a bailout.

The company, which serves about 16 million people in London and the South East, is battling a funding crisis that could see it run out of cash by March.