Posh Spice allegedly turned down a recent overture from Paris Hilton to be the socialite/convict's newest best friend.

Now, she's apparently got to be concerned about having one of Hollywood's other bad girls as an enemy.

According to a report in London's Sun newspaper, Lindsay Lohan is so confident in her ability to get to the real root of David Beckham's nickname (that would be Goldenballs for you soccer neophytes), that she's got $50,000 riding on her ability to successfully bed Beckham.

And while not wanting to appear to be supporting that kind of wanton home-wrecking, that would be an infinitely sexier gambling scandal than the one currently plaguing the NBA.

Lohan has even allegedly given herself a December deadline to do the deed, a date that coincides with the soon-to-be-reunited Spice Girls' world tour.

But given, um, recent events, she might have to forfeit the bet ... unless the California penal system is particularly lax when it comes to the subject of conjugal visits or Lohan can get her case transferred to L.A. County Sheriff Lee Baca's jurisdiction.