The textile, which was used at the coronation of Edward VII, is going under the hammer at the Edinburgh auction house tomorrow and is estimated to fetch up to £15,000.
It was gifted to the Cathedral's Kirk Session upon the death of Charles Hepburn, who bought the carpet in 1938. The Church of Scotland said the cathedral initially planned to pay to keep the carpet from deteriorating further but was advised its charity status would not allow funds to be spent on conserving "heirlooms and artefacts".
Dr Scott Hepburn, Mr Hepburn's nephew, has accused the Church of "selling off the family silver".
Picture: Gordon Terris