Applications to erect two-metre fences round open space in Hill Head have now been rejected by planing officers.
But the Lib Dems have found that other green spaces could be under threat.
The green north of Springfield Way has been enjoyed by everyone for decades since the estate was built in the 1970s, but two sections of the land were recently sold at auction.
Those sections, though listed as public open space in Fareham’s local plan, were never owned by Fareham Council.
Agents for the applicants said they wanted the fence to prevent vandalism, anti-social behaviour and fly-tipping.
Councillor Jim Forrest says: “I don’t recall any of these issues arising in this space in the 25 years I’ve lived in Hill Head. A fence would destroy the view and prevent lawful use.
“Scores of residents wrote to the Council to say the same, and happily the plans have been quashed.”
But Jim, who is Lib Dem spokesman on planning and development, adds: “This could have worrying implications for Fareham as a whole. I’ve made inquiries and found there are other sites around Fareham where land currently in use as open space is still in private hands."
“I’ve put a question to the Council to ask how many such sites there are and what can be done to protect them.”