Reservoir will cost customers £1.9bn over 65 years

The £1.9bn running cost is on top of between £5.5bn and £7.5bn to build the facility

A huge new reservoir near Abingdon will cost £1.9bn to run for its first 65 years, according to the latest Thames Water report.

The company previously revealed that the estimated price for building the reservoir has risen significantly, from £2.2bn to between £5.5bn and £7.5bn.

Thames Water insists that operating costs have not risen alongside the capital cost.

It says the reservoir remains the "most cost-effective option" to secure water supply for 15 million people in the South East.

Customers of Thames Water, Affinity Water and Southern Water will pay for the new reservoir through their bills.

Previously, the company gave a lifetime running cost - over 250 years - of around £4.8bn.

Thames Water says that figure is not comparable with the new running cost of £1.9bn over 65 years, because it is based on higher usage of the facility.

Thames Water's Strategic Water Resources Director, Nevil Muncaster, said: "The cost of operating the reservoir has not increased; it is simply that our most recent report used numbers based on much higher potential use of the reservoir, which is prudent practice when managing a project of this scale.

"We are seeing more frequent and longer droughts and need to plan for the reservoir potentially being used more often if needed.

"We remain confident that the reservoir is the most cost-effective option for securing water supply for 15 million people across the South East."

The Liberal Democrat MP for Didcot & Wantage, Olly Glover, said the new running cost figure would add to resident's concerns about the project and the impact on bills.

He said: "Thames Water bills have already gone up significantly and people just don't have faith that that money is going to be well spent, because there's already so many water leaks and so much sewage dumping.

"I share those concerns."

Thames Water says it plans to put in a planning application for the South East Strategic Reservoir Option (SESRO) next year.