Critics of plans to build more than 100 new homes on protected parkland in south London have lobbied the mayor.
The park is in line for a £100m revamp
Crystal Palace Park, designated as Metropolitan Open Land but said to be rundown in parts, is at the centre of plans for a £100m facelift.
The London Development Agency (LDA) is looking at selling two pockets of land to developers, to fund restorations.
The Crystal Palace Community Association handed in a petition to the mayor on Wednesday.
Chairman John Payne said many people were unaware that the proposals included plans for "luxury housing".
The group, backed by some environmental campaigners, say they have collected 8,000 signatures.
"There isn't a day goes by when people aren't asking to sign the petition," he told the BBC.
"If the LDA succeed in their plan to sell off this famous London parkland, the precedent would be set that would threaten every park and open space in the country."
The park is owned by Bromley Council but is set to be handed to the LDA in the next few years to be given a revamp.
In March, plans to build flats near the Crystal Palace Triangle were dropped, following public consultation.
But between 140 and 170 flats could still be built at two other sites - the Rockhills Gate entrance to the park and a site in the north-east corner.
"These sites are an enclosed caravan park and an area where houses were bombed during the war. Neither of these sites are currently accessible to the public," said a spokesman for the LDA.
"We are not planning to build housing on accessible parts of Crystal Palace Park.
"We are committed to increase the amount of green open space in the park."