Cllr Barby Dashwood-Morris was also ordered to pay £40,000 costs by the District Judge at Brighton Magistrates Court on Wednesday.
Dashwood-Morris was prosecuted by Wealden District Council for causing “irreversible changes” to the 14th Century building known as The Priest House in Hellingly.
Alterations included the creation of a full height entrance hall through removal of ceilings and partitions, affecting the area for where there is anecdotal evidence for a priest hole; glazing of a partition; and removal of the barley twist bannisters and associated bannister rail to the staircase and replacing them with glazed panels.
Dashwood-Morris pleaded guilty to six charges of causing works to be executed, for the alteration of the Grade II listed building, without obtaining the proper consent from the Council where she was chairman of the Planning Committee South from 2011 until 2013.
Kelvin Williams, Wealden’s District Council’s Head of Planning and Environmental Services, said: “The changes to this important listed building came to light when the owners attempted to sell the property.
“Owners of historic properties should be aware of their responsibilities to the property and future generations.
“We will take action when necessary to protect the important heritage of our District.”