The blonde actress - who married the singer in August 1992 - blames Bob for dreaming up the idea when the pair were being interviewed, and she said it was a case of "if only" her husband could last that long.
She told the Daily Telegraph newspaper: "Sting said that 21 years ago. He has just turned 60, and I imagine [the tantric story] will carry on going until he drops.
"Do you know who I blame for that? Bob Geldof. Him and Sting had gone to do an interview with a rock journalist, and the interview turned into a drinking session.
"At one point, the journalist asked how long they could go for, and Geldof said he was a three-minute man, but, as Sting did yoga, he could probably go for hours. And Sting said, 'Well, haven't you heard of tantric sex?'
"So Sting explained that it is all about being intimate, about caring for your partner, really engaging in intimacy before you, you know... have sex. And that's the premise of tantra, really. It's simply engagement with your partner."
Trudie - who has four children, Bridget, Jake, Eliot, who is known as Coco, and Giacomo, with Sting - admits the joke is now wearing thin after all these years.
She added: "At the time I thought it was very amusing but then it sort of became a cause cÃ©lÃ¨bre. The tantric hours got extended and, suddenly, I was doing it all day long. Well, if only!"
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