LONDON (Reuters) - The Vatican was "utterly let down" by an Italian financier over the Catholic Church's botched investment in a high-end London property, a judge ruled on Friday following a trial at which a senior aide to Pope Francis gave evidence.

Italian financier Raffaele Mincione's case centred on the Vatican's investment in a west London property, which it ultimately sold at a loss of about 140 million euros ($147 million) in 2022.

He sued the Vatican at London's High Court, seeking declarations that he acted "in good faith" in relation to the deal.

The investment led to a long-running corruption trial which exposed infighting and intrigue in the highest echelons of the Vatican, ending with the conviction of a cardinal, Mincione and others in December 2023.

Mincione is appealing against his conviction and has also lodged a complaint with the United Nations' human rights watchdog.

Archbishop Edgar Pena Parra, a senior aide to Pope Francis, gave evidence at the trial of Mincione's lawsuit last year.

Mincione and companies in his WRM Group sought various declarations about their agreement with the Vatican, including that they "had acted in good faith in and about the transaction and the negotiation and execution of the contractual documents".

Judge Robin Knowles said in a written ruling: "On the facts shown at trial the claimants fell below the standards of communication with the state (the Vatican) that could be described as good faith conduct."

He rejected the Vatican's allegations that Mincione and his companies were involved in a conspiracy to defraud the Vatican, but added: "The state had reason to consider itself utterly let down in its experience with the claimants.

"The claimants made no attempt to protect the state from fraudulent bad actors."

Mincione welcomed the ruling, saying in a statement: "I hope the judgment can lay to rest once and for all claims that I am dishonest, or a fraudster, or a criminal."

The Vatican did not respond to a request for comment.

(Reporting by Sam Tobin; additional reporting by Joshua McElwee; editing by Giles Elgood)