"The son [of the assassinated Ali Khamenei] is either dead or in extremely critical condition," he claimed.
"We haven't heard anything about him. He has disappeared."
The absence of Iran's new supreme leader has fueled speculation that he is severely injured, the FT noted.
Tehran insists that Mojtaba Khamenei is safe and feeling well.
Iran's Assembly of Experts elected Mojtaba Khamenei, the son of the late Ayatollah Ali Khamenei, as the country's new supreme leader on March 8.
Mojtaba Khamenei was injured at the beginning of the U.S. and Israeli special operation, the American newspaper NYT wrote on March 11. He has not appeared in public due to his injuries and security concerns, and is located in a secure location with limited communication, according to the publication's sources.
Iranian Foreign Ministry spokesperson Esmaeil Baghaei confirmed the new Ayatollah's injury on March 12.
"He is injured but feeling well," the diplomat claimed.
Mojtaba Khamenei survived the U.S. and Israeli airstrike that killed his father, Ali Khamenei, because he stepped out into the garden a few minutes before the house was struck by missiles, the British newspaper The Telegraph wrote on March 17.