William Shatner has insisted Prince William is "wrong" about space travel after the royal said the focus should be on repairing this planet - not blasting off to others.
The Duke of Cambridge's comments were aired a day after Star Trek actor Shatner became the oldest person to go to space.
The 90-year-old made history when he launched into the skies in a rocket built by billionaire Amazon boss Jeff Bezos’ Blue Origin, before returning safely to Earth.
Speaking about his earthshot prize (a climate change initiative) the Duke of Cambridge BBC's Newscast the "world's greatest brains" should be focused on "trying to repair this planet" rather than blasting off into space.
He added: "It really is quite crucial to be focusing on this (planet) rather than giving up and heading out into space to try and think of solutions for the future."
The royal, a trained pilot, said he had no space travel ambitions himself, and questioned the carbon cost of space flight.
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William did not mention Mr Bezos by name in the interview.
Mr Shatner reacted to the royal's comments in an interview with Entertainment Tonight, in which he described his space trip as akin to a "religious experience."
The star said of the royal's remarks: "He's a lovely, gentle, educated man, but he's got the wrong idea."
Watch the Duke of Cambridge discuss climate change on ITV's Prince William: A Planet For Us All:
Mr Shatner said he hoped the energy resource industry and technology leaders would build bases above the Earth, to divert the activity away from the planet's ecosystem.
He suggested the effort needed figures as "rich" as Jeff Bezos to take an interest in space exploration so the ambition could be realised.
The actor added: "The prince is missing the point. The point is these are the baby steps to show people (that) it's very practical. You can send somebody like me up into space."
Mr Shatner said he also agreed with the royal's plea for innovators to focus on the problems on Earth rather space exploration.
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He added: "So fix some of the stuff down here... But we can curl your hair and put lotion on your face at the same time."
The duke was being interviewed about climate change ahead of his inaugural Earthshot Prize.
Earthshot will honour five winners with £1 million prizes for solutions to the planet’s environmental problems and will run until 2030.
Mr Shatner's comments come after it emerged the Queen appeared to suggest she is irritated by a lack of action in tackling the climate crisis.
The monarch's remarks surfaced in clips of a conversation filmed on a phone camera during a trip to Cardiff for the opening of the Welsh Senedd on Thursday.