The BBC's star science presenter Brian Cox thought he might have a scoop on his hands when he trained his telescope at a newly discovered planet in search of alien life.
But the professor said his hopes for an exclusive were brought back down to earth after he was told by the BBC that impromptu extraterrestrial contact would break health and safety guidelines.
Cox, the former pop star turned particle physicist, wanted to use the Jodrell Bank Observatory in Cheshire to listen in to the planet, Threapleton Holmes B, on his BBC2 series Stargazing Live.
"We decided that we'd point the Jodrell Bank telescope at the planet that had been discovered by these two viewers and listen because no one had ever pointed a radio telescope at it and you never know," said Cox.
"The BBC actually said, 'But you can't do that because we need to go through the regulations and health and safety and everything in case we discover a signal from an alien civilisation'.
"You mean we would discover the first hint that there is other intelligent life in the universe beyond Earth, live on air, and you're worried about the health and safety of it?
"It was incredible. They did have guidelines. Compliance."
Cox made the comments in an interview on the BBC Radio 6 Music breakfast show on Wednesday.
Presenter Shaun Keaveny told Cox: "The idea that intelligent life could be discovered and it might swear and that's why we wouldn't broadcast it – it's such a brilliant BBC thing, isn't it?"
Cox's co-presenter on Stargazing Live, Dara O Briain, later suggested on Twitter than Cox was employing some "comedic licence".
"Actually not banned," said O Briain. "We still did it live on-air and heard nothing, sadly."
He added: "It's still funny! It's just that the BBC don't have an ET policy. Neither did the UN. Only the Vatican did."
The BBC's health and safety regime has long been a bugbear of another BBC2 star, Top Gear presenter Jeremy Clarkson. Some BBC staff also took issue with the stringent regime introduced in the wake of the "Sachsgate" scandal in 2008.
Cox, the one-time keyboard player with 1990s pop group D:Ream, became a household name presenting BBC2's Wonders of the Solar System and followed it up with Wonders of the Universe and a new BBC2 series, Wonders of Life.
He recounted another incident on Stargazing Live in which his BBC colleagues appeared underwhelmed by the prospect of discovering alien life. The programme had considered asking viewers for help in the search for life on Mars, he said.
"There are lots of maps of Mars and lots of things that people can do looking at them that computers can't. We were thinking of ... looking for signs of geological activity which might point to life on Mars," said Cox.
"Someone from the BBC said to me, 'Would there have to be a prize if someone discovered it?'. [I said], 'What do you mean? You're going to say to someone, you discovered the first evidence for alien life beyond Earth – and here's a book voucher as well?'.
"You think that's going to make it better? 'You're going to go down in history with a Nobel prize – book tokens or Nectar points?'."
Stargazing Live, which Cox presented with comedian Dara O Briain, returned for a second series at the beginning of this year and was one of BBC2's most popular shows, with around 4 million viewers.
A BBC spokeswoman said: "In making the series there were many light-hearted conversations, one of which was about how different organisations might react to the discovery of alien life."
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