The 35-year-old actress, who played Daenerys Targaryen in the hitshow, revealed she has spoken to Harrington about the upcoming project.
Speaking to theduring a recent interview, Clarke explained Harington has been heavily involved in creating the new series.
“He has told me about it. And I know it exists. It’s happening,” she said.
“It’s been created by Kit as far as I can understand, so he’s in it from the ground up. So what you will be watching, hopefully, if it happens, is certified by Kit Harington.”
The actress also suggested she won’t be joining Harington in the spin-off as she said she was “done” with the Game of Thrones franchise.
Harington has been approached for comment about the spin-off claims.
Harington’s character Jon Snow learned in the final season that his real name was Aegon Targaryen and that he also may also have a claim to the Iron Throne.
His character eventually travelled north after he killed Daenerys .
Clarke’s remarks come shortly before the new HBO show House of Dragon is due to be released on August 21.
Set three centuries before the original Game of Thrones series, the new show will focus on the Targaryen family and the civil war between them.
Reflecting upon the new show, Clarke said she was fascinated to simply watch House of the Dragon as a viewer.
She added: “I’m going to watch this as a fresh viewer because it’s [set] a be-jillion years before our show, so it’s going to feel different.”
The unnamed HBO spin-off featuring Harington joins a number of other Game of Thrones universe projects in development.
Among them is 9 Voyages that will follow the character Corlys Velaryon.