The Department of Infrastructure says revealing how much it charges a charity to rent land in Ramsey could undermind future negotiations.
A Freedom of Information request to the department asked how much it charged the Manx Wildlife Trust for two plots at the Hairpin Woodland Park.
But the DOI says the information is commercially sensitive and won't be released.
Earlier this month, the charity said it had signed a 95-year lease for the land, which forms part of a Biosphere project.
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