Residents in Didcot fear parkland behind their homes could be sold to travellers.
Land behind Lincoln Gardens, Mansfield Gardens and Campion Hall Drive is due to be sold at auction on October 5.
The land is currently owned by developers Wates Group, which built the adjoining houses in the early 1980s.
But because it can only be used as public open space, residents are concerned about the motives of any prospective buyer.
"Residents are concerned the land could be purchased by travellers, like the land at Hadden Hill," said Didcot town and district councillor Mike McNulty.
"Why would anyone want that land? That's when the debate opens that someone might purchase the land for something that is unacceptable."
Mr McNulty said residents themselves had even talked of buying the land, which has a guide price of more than £25,000.
He added: "The residents have a right to look to the local authority to protect their interests. The residents certainly should not be expected to purchase the land."
Mr McNulty contacted South Oxfordshire District Council chief executive David Buckle on the matter and asked if the council could intervene or buy the site.
Mr Buckle said he understood residents' concerns, but said the council would not bid for the land.
He added: "We are reviewing our land at the moment and divesting any land with no strategic purpose. There is no strategic reason to buy this land."
Despite the area being designated as public amenity space in both the original planning permission and the district council's 1984 local plan, it was never transferred to a local authority.
In the existing local plan there is no mention of the land, or its classification.
But Mr Buckle said any prospective purchaser would have to retain the land as public open space. "If it was not used as public space they would be in breach of our planning policies," he warned.
Mr Buckle added that planning law and legal agreements at the time of the original planning permission were not as refined as they are now, and that might be one reason the site was not transferred to a local authority.
A spokesman for Wates Group said the company was currently "consolidating its property portfolio".
She added: "We have several small pieces of land we do not have a use for."
The land will by auctioned by Ward and Partners in two plots, with a combined guide price of £25,500.
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