Leading Liberal Democrat Paul Elgood has attacked as "ludicrous" plans to site a rubbish burner in an area of outstanding natural beauty.
The Brighton and Hove Council Lib Dem leader made the comment even though the plans have been proposed by East Sussex County Council, led by party colleague David Rogers.
Waterhall Valley, north of Patcham, has been chosen by the county council's ruling Cabinet, even though the authority's own officers have said North Quay at Newhaven would be a better site.
East Sussex has been working with Brighton and Hove on a waste plan but they cannot agree on some locations, notably for an incinerator to produce energy from waste.
Coun Elgood said rubbish burners should not be placed at Waterhall or anywhere else in the area.
He added: "We are not convinced incineration is the right route to take. The health risks are still not quantified."
Coun Elgood said: "With the Labour-controlled borough council ruling Waterhall out of consideration as a park-and-ride site, then this key area of downland in an area of outstanding natural beauty must remain open space.
"We do not see any case for building north of the bypass in this area, regardless of use, and will oppose any plan to do so."
But Coun Elgood blamed the Brighton and Hove Labour leadership for trying to dump its waste crisis on neighbours and not doing enough to encourage recycling. He said: "The message from East Sussex is clear - that Brighton and Hove should sort its own waste problems out - and we can hardly blame them."
Brighton and Hove environment councillor John Ballance said the decision by East Sussex was peculiar.
He said Waterhall was not identified for development in the council's local plan and warned of problems if there was any more delay in the two councils coming to an agreement on waste disposal.
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