Campaigners are fighting to preserve an open space earmarked as a possible site for a sewage treatment plant.
Southern Water has suggested eight possible locations for a new plant following last year's rejection of a scheme at Portobello, near Telscombe Cliffs.
Two of the proposed sites are in Sheepcote Valley, a large area of open space in East Brighton, which used to be a rubbish tip.
A third is at nearby Black Rock on land earmarked by Brighton and Hove City Council for leisure.
Bernard Evans, secretary of the Friends of Sheepcote Valley, said: "Our group of volunteers has worked with the council to retrieve the valley from its historic use as a dumping ground for waste and chalk.
"It is an area of great value for wildlife, flora, fauna and human recreation. It is inconceivable either of the two sites could be acceptable."
Labour councillor Gill Mitchell is also opposing all three sites along with two other prospective candidates for the new East Brighton ward, Warren Morgan and Craig Turton.
Mr Morgan said he would work with residents to fight the proposals all the way.
Mr Turton said Black Rock was out of the question because it was too close to people's homes.
He said: "The two Sheepcote Valley proposals are also unrealistic given this is an important environmental area for wildlife and plants.
"These proposals would also mean the temporary loss of the football pitches."
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