He looked sheepish as the show's presenters joked that they'd be sure send Posh the clip.
Paul went on to reveal that years later he "pied" Becks when the global superstar approached him for a selfie at a work event.
Reflecting on how close they became during tour, the sports pundit shared: "He kind of latched on a bit with us, we were like: 'David Beckham, what a guy' and so we kind of hung around with him.
"He thought my mate Rich was hilarious as he's a proper lad, so we saw quite a lot of him on that tour situation."
Paul went on: "Then I saw him on a job a few years later, and I didn't got and see him because you get busy, so I'm trying to get my guest in and I see David walking over and I was like: 'He's recognised me'.
"He's like: 'Alright Paul, how's it going?', the nicest guy, he said: 'Come on, let's get a selfie and send it to your Mel' and I was like: 'I ain't got no time!'"
Everyone laughed as Paul exclaimed: "I pied off David Beckham!"
Paul also said it was hard having a megastar sister growing up, and he was just 16 years old when Mel shot to fame in the '90s.
He shared: "It grinded on me. I am not going to say it was difficult but it was quite hard and people were taking the mickey all the time."
Meanwhile, Mel revealed that she feared being "too relaxed" while filming Celebrity Gogglebox with her "annoying little brother".
She joked: "He is going tho throw me under the bus and expose all my secrets."
Celebrity Gogglebox kicks off on Friday 4 June at 9pm on Channel 4.