Beckham was omitted from coach Stuart Pearce's squad despite playing a key role in the team that won the Games for London.
Beatles legend Sir Paul said: "I would've thought Beckham would be first choice because of his huge contribution to getting the Olympics. But some idiot decided otherwise.
"I feel a bit sorry for the three over-23s because we're going to be looking at them and saying 'That should have been Beckham.' He's a national hero, a crowd-puller."
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