Lord Carey, the former Archbishop of Canterbury, says that a tabot held by Westminster Abbey should be returned to its native Ethiopia.
He told The Art Newspaper he was "astonished and saddened" that the Abbey has no plans to return the item.
In the Ethiopian Orthodox Church, tabots are a type of plaque made of wood or stone that represent the Ark of the Covenant and the Ten Commandments.
They are considered highly sacred and can only be seen by priests. They cannot be put on display.
It follows calls by Lord Carey last month for the return of 11 tabots held by the British Museum to Ethiopia as a "matter of faith".
"It is cruel to deprive believers of access to faith and tabots are essential to Ethiopian worship," he said.
Westminster Abbey is a 'royal peculiar' and therefore falls under the jurisdiction of King Charles III.
The abbey said in response to his comments that the tabot was being kept in a "very sacred place" in the church.
"Westminster Abbey is very aware of the importance and significance of the Ethiopian Tabot which we have in our care," a spokesperson for the abbey told The Telegraph at the time.
"It is kept in a very sacred place within the church, properly covered and hidden from view. We have no current plans to change these arrangements," they added.
The tabot came into the hands of the abbey as a donation by Captain George Arbuthnot of the Royal Artillery after it was looted at the battle of Maqdala (Magdala) in 1868.
Westminster Abbey has been contacted for comment.