A key group of environmental advisors has backed a site for a multi-million pound sewage treatment works.
The disclosure by the Sussex Area Advisory Group has sparked protests from residents fighting to protect parkland near their homes.
The group has said the site, proposed by Southern Water in the lower part of Sheepcote Valley, at the crossroads of Wilson Avenue and Roedean Road in East Brighton, is the most promising environmental option.
Plans to build the works in any part of the valley have been condemned by residents.
They say the site is too near residential properties and a works would ruin the valley, which has been set aside for leisure purposes.
The advisory group studied all eight sites Southern Water has put forward between Newhaven and Shoreham for the works it needs to build to improve the treatment of 95 million litres of wastewater generated in Brighton and Hove each day.
The company insists it does not have a preferred option and has submitted the eight for discussion before putting in a planning application.
The advisory group said the Lower Sheepcote Valley site was the best because pumping sewage to and from other sites seemed unsustainable.
At other sites, long pipe lines would have to be built along the coast and into the Downs.
The group is made up of local authority representatives and people interested in the environment from across Sussex.
It makes representations to the Environment Agency, one of the authorities involved in making the final decision on where the works will be built.
An agency spokeswoman said: "We would take note of what the group says but we are not bound by its recommendations."
News of the group's backing shocked people who want to see the valley protected.
Doug Gibson, of the Friends of Sheepcote Valley, said: "I am appalled and horrified they have come out in favour of this site.
"It proves we need to fight to protect this valley."
Councillor David Smith, who has been leading the fight against the works being constructed in East Brighton, said: "The sites here are totally unsuitable.
"There would be huge disruption to residential areas.
"I am convinced the works should be built on a brownfield site in Shoreham or Newhaven."
Southern Water representatives presented their proposals to the Friends of Sheepcote Valley on Sunday.
A company spokeswoman said: "It was a productive meeting.
"We welcome feedback during the public consultation, which ends on Monday.
"After this, the project team will look to choose the preferred site on which to make a planning application.
"This will be based on many factors, including proximity to the existing pumping stations, planning restrictions, environmental matters and sustainability."
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