The Diocese of Truro is seeking legal advice to see if it has any cause for redress after losing out from the sale of antique books.
The Diocese sold the collection in 2006 to the highest bidder
A dealer bought the collection for £36,000 in 2006. However the books, some dating back to 1470, have just sold at Sotheby's for £500,000.
Prior to the sale last year, the religious books had been in the Bishop Philpotts Library in Truro.
The library was set up in 1856 for the benefit of clergy in Cornwall.
In 2002 the Bishop Philphotts Library approached the Diocese of Truro to see if the trustees would be happy for them to sell a small proportion of its extensive collection.
The trustees approved the move.
A spokesman for the Diocese of Truro, Jeremy Dowling, said: "The Library paid for a valuation in 2002 and was told the books were worth £20,000."
The spokesman added that when it was approached by a London book dealer in 2005 and again in 2006 "a £16,000 increase over three to four years seemed reasonable."
The London bookseller put in the highest bid for the collection at £36,000.
The Diocese only realised it had lost out when a single volume recently made £78,000 alone at a Sotheby's auction.
The Diocese of Truro, who is acting on behalf of the Bishop Philpotts Library, is now seeking legal advice on the situation and is unable to comment.