The future of a piece of green open space in Bury St Edmunds, which campaigners had hoped would be safeguarded from development, has been plunged into uncertainty.

The Bury St Edmunds Water Meadows Group was formed to protect a patch of land known as the Leg of Mutton, to the west of Rougham Road, which it believes should be fully preserved for future generations as a “green lung for Bury”.

Planning inspector Roger Clews, who led a public inquiry into St Edmundsbury Borough Council’s draft Vision 2031 local plan documents, had recommended the land be designated for “amenity public open space for informal outdoor recreation” and any building should be directly related to that use.

This would prevent sports pitches or a fitness centre from being built at the site, which is a 15-hectare plot of agricultural land owned by a private trust.

But the future of the site has become less clear as it emerged that the borough council is looking to object to Mr Clews’ recommendation.

A report which went before a committee meeting last week, and which needs to ratified by the borough council’s cabinet, said: “Policies in a local plan have to be deliverable and, as such, viable and it is considered unlikely that, as a result of this modification, the landowner would receive sufficient return from the uses specified in the policy to enable it to proceed.

“The council also considers that the policy, or supporting paragraphs, should define the meaning of ‘informal recreation’ in order to provide some certainty going forward as to what would be acceptable on the site.”

Andrew Hinchley, chairman of the Bury Water Meadows Group, said he was “flabbergasted” that the council was seeking to object to the inspector’s proposed changes.

He added the council’s objection could put a spanner in the works for the group’s Heritage Lottery Fund bid, which it is yet to submit, to purchase this land for the community.

He said: “It’s a big shock. We are very hopeful the inspector will stand his ground and that’s why I really want to focus on appealing to people to write in and support the inspector’s recommendation.”

He said the campaign group was looking to raise a minimum of £500,000 to purchase the land.

Green councillor Julia Wakelam said: “This land has been farmed for 500 years. The landowners can continue to farm it. No one is forcing them to turn the land into amenity public open space.” William Stanton, director of Pigeon Investment Management Limited, said the company was still promoting the site for “formal recreation” uses.

“Obviously it’s a commercial asset for them [the landowners] and the council has quite rightly said it has to be made viable for someone to do something,” he said.

A borough council spokeswoman said it was seeking an explanation of what “informal recreation” is and was also asking the inspector to consider whether the modification would make the proposal viable for the landowner to sell it for use as public open space.

She said the council supported “recreational use” of the Leg of Mutton site, adding: “If the permitted uses of the land add no extra value, we are concerned that the owner will have no incentive to sell, making both the council’s and community’s aspirations very difficult to achieve.”

The consultation on the inspector’s modifications ends on May 30. To comment visit the borough council’s website.