The X Factor judge is organising the celebratory gig, and Mel B hinted the girlband could be performing while speaking on Australian TV.
While Mel B, Melanie C, Geri Halliwell and Emma Bunton are all prepared to reunite, Victoria Beckham doesn't want to be a part of it, according to the Sunday Mirror.
"All the girls are desperate for some Spice action except Posh who is simply too busy - she loves the girls and wants to support them and the fans but doesn't see how she has the time when her fashion business is so successful," a source said.
"She has a very small team that she is hands-on with all day, every day. Every spare minute she has is spent with her children."
Beckham was previously said to have declined an offer to perform with the Spice Girls at the opening ceremony of the 2012 London Olympics for similar reasons.
Watch Mel C discuss the Spice Girls musical below: