The British girl band - which also includes members Emma Bunton, 36, Mel C, 38, Geri Halliwell, 40 and Mel B, 37 - are reportedly set to announce their reunion within weeks and are thinking about recruiting a new member to take the fashion designer's place in the group so they can continue to make new music and tour.
A source told the MailOnline: ''The girls are going it alone without Victoria. They are keen to get back together and were trying to work out if they could do it as a four-piece. I think they know this is the last chance for them to get the band going again.
''But the Spice Girls as a foursome is not going to get them another record deal or sell out big venues. They need an extra cherry on the cake. And the cherry on the cake would be if they replaced Victoria.
''And that leads to the next question: who do they replace her with? At the moment it's all being done in a very cloak-and-dagger way and not through official channels.
''At the moment they're thinking who, out there, who's been in a another band, could be Victoria. There would be interest in a television series, but I think they're keen on someone with industry experience rather than discovering a new star.''
When asked to comment on the speculation, a spokesperson for Victoria would only say: ''Victoria respects all of the girls and will always support them all personally and professionally.''
Among those rumoured to be in the running to replace her is former Sugababes star Heidi Range, 29, who is already close friends with Emma.
Last week Victoria and her family posed separately from the group and hid away during the 'Viva Forever!' after-party.
The 38-year-old fashion designer arrived at the marquee on the banks of London's River Thames on Tuesday evening (11.12.12) with her husband David, 37, and sons Brooklyn, 13, Romeo, 10, and seven-year-old Cruz after the opening of the Spice Girls musical at Piccadilly Theatre but instead of joining the rest of her bandmates on the dancefloor, they sat quietly in the corner.