Highland Titles offers square foot patches for £29.99 on a 750-acre area known as the Keil estate, and tells buyers that owning the land allows them to adopt the title Laird, Lord or Lady of Glencoe. It is the brainchild of Professor Peter Bevis, an English biologist, and his wife, Laura, who bought the land in 2007.
However, they have been ordered to make clear to customers that buying the land does not give them a genuine title following a probe by the Advertising Standards Authority (ASA).
Douglas Wilson, a director at Highland Titles, claimed they had been targeted by a disgruntled customer.
He said: "The ASA ruling is incredible. We have made small changes to the website in light of this but we feel aggrieved."