As part of a consultation on the Bristol Central Area Plan, residents are being asked their opinions on regeneration of St Mary-le-Port, popularly known as Castle Park.
The area plan talks of redevelopment of outdated and unused buildings to enhance the area and recreate the traditional street layout lost in the Second World War.
But getting developers on board could lead to loss of green space for residents.
The Castle Park Users Group, which tried and failed to get the space registered as a town green in 2008 and calls the park "a haven for local residents, city centre workers and shoppers alike" has urged local people to object.
A statement on its website reads: "Castle Park Users Group is not against redevelopment of the St Mary-le-Port area so longs as buildings do not encroach on the park or mean the felling of large trees. What is currently Castle Park should remain Castle Park.
"Many would like to see the expansion of the park around the St Mary-le-Port, however given the high monetary value of land in the city centre this is extremely unlikely to happen for the foreseeable future."
Castle Park was created after World War Two from an area of land which was bombed. The council bought the land and promised it to the people of Bristol. Despite this it sold some of the land to the Bank of England and Norwich Union in the 1960s. It is these buildings that the council refers to in its plan.
The consultation runs until 18 October.