Campaigners have vowed to continue their fight against a huge reservoir near Abingdon.

Last week the Government backed Thames Water's management plan for the next 50 years, which includes the proposal for the new reservoir.

It would be situated south west of Abingdon and produce up to 270 million litres of water per day, providing additional water supplies to 15 million people. 

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It is set to be as big as Gatwick Airport, holding 150 billion litres of water, and has faced repeated local opposition.

The Secretary of State for Environment, Food and Rural Affairs, Steve Reed, approved the Water Resource Management Plan (WRMP).  

But campaigners led by GARD (Group Against Reservoir Development) say they will continue to oppose the new facility.

Spokesman Derek Stork has written to Mr Reed seeking a public inquiry.

More than 3,00 people signed a petition led by GARD and countryside charity the CPRE calling for the inquiry.

Mr Stork wrote to Mr Reed: "Given the numerous unresolved issues in the plans, as well as the significant public interest around the proposals, we are writing to request that you reverse your recent decision of 4th September and call a public inquiry into the plans and do not allow the plans to be published without proper, rigorous, and transparent scrutiny."

(Image: Thames Water) Following the government announcement, Mr Stork told the Abingdon Herald: "This news will be greeted with astonishment and deep resentment in the areas of South Oxfordshire that would be seriously affected if this hugely expensive and damaging reservoir goes ahead.

"There is astonishment because the Secretary of State has overruled his Environment Agency advice from last December that the Thames Water draft plan should be rejected and returned for modifications.

"The agency recommended these modifications because of its concerns about the huge reservoir's resilience to drought and its view that Thames Water had not demonstrated that the plan including the reservoir was the best value for money."

Mr Stork added: "It is also astonishing that the Secretary of State should allow a scheme to progress to the next stage only one week after a public consultation had closed and before results had been analysed.

"As one can see from the county, the Vale district and the Abingdon Town Council websites there was widespread opposition from these organisations to the plans.

"GARD submitted a critical response of over 100 pages, which has clearly not even been looked at, and we are aware of opposition responses from campaign groups and parish councils."

Chris Weston, CEO of Thames Water, said earlier: “I welcome the Secretary of State’s approval of our plan, which is a vital step as we work to secure future water supply for millions of people across the South East.    

“In delivering this plan we will invest in new world-class infrastructure projects, continue to drive down leakage and reduce demand for water.

"In turn this will significantly reduce our reliance on groundwater sources that draw from chalk streams, protecting the local environment.” 

Mr Reed concluded there was a strategic need for the new reservoir, known as the South East Strategic Reservoir Option (SESRO), and the Teddington Direct River Abstraction project.

The Teddington scheme will provide up to 75 million litres of water per day in drought conditions.