Campaigners have warned that the decision to allow a community stadium at Falmer could pave the way for development of the city's remaining green spaces.
The Seagulls' new ground will be built in an Area of Outstanding Natural Beauty (AONB) and conservationists fear that similar land, considered sacrosanct until now, could follow suit.
Residents are fighting proposals for a park-and-ride scheme in Patcham.
The council has identified two possible sites, one of which it wants to turn into a 900-space car park for park and ride.
Both are within an AONB and residents hoped this would give them some protection from bulldozers.
Dave Tyrrell, chairman of Patcham Against Insensitive Destructive Development, said: "If we weren't in a marginal constituency with three Labour candidates, it probably would not have gone through but it has set a precedent. It is a green light to develop on green land."
Mr Tyrrell has written to Carolyn Dwyer, the council's assistant director of the environment, asking questions about the proposed park-and- ride sites at Braypool and Patcham Court Farm.
He wants to know why no other sites outside the city are considered, the impact a 900- space car park will have on the environment and how the park- and-ride will affect views from the proposed South Downs National Park.
Many residents of Patcham are angry the council is considering concreting over people's homes to make way for a giant car park for visitors.
Some councillors opposed to the site believe it will be used by people commuting down the A23 to work in the city and not by tourists.
Mr Tyrrell added: "We have tried to put in as many questions as we can and it's a long list. They need answering. "
Patcham residents fighting the plans are organising a march on Hove Town Hall on Thursday, November 24, at 4.30pm to coincide with the full council meeting.
Environment councillor Gill Mitchell said: "We care very much about Brighton's green spaces.
"The proposal for a community stadium at Falmer was subject to a full planning process.
"It went through a public inquiry and was granted by the Secretary of State. It doesn't set any precedent for other areas.
"Both proposed sites for the park-and-ride continue to be looked at in tandem and a decision will be made in December."
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