Campaigners in Littlehampton are trying to force a council to designate a patch of land as a village green to stop it from being built on.The land north of Littlehampton Academy is used by hundreds of people every day to walk dogs, cycle and play sport.
But campaigners believe West Sussex County Council wants to build new housing there, something the authority has dismissed as speculation.
The village green application will be decided on by the county council.
Chris Hughes, who is leading the campaign, said the community would be "devastated" if the field was built on and was worried about a conflict of interests.
He said: "There does seem to be a link there and we don't have any vote ourselves, so what we're asking people to do is write in to the council, especially if they use the field, to support our application."
He said if the field was built on it would force people to travel to other parts of the town.
"For people in this area they would have to resort to getting into cars and driving to other areas [to use a park] so it's regularly used by maybe up to 200 people a day."
For the land to be designated as a village green, campaigners will have to prove it has been occupied for recreational purposes for 20 years.
A West Sussex County Council spokeswoman said she was unaware of any intention to build on the land.
"An application was received earlier this year to register the county council's land to the north of Littlehampton Academy as a town or village green," she said.
"This is currently being investigated and will be determined this autumn, as part of a statutory process, by the county council's rights of way committee."