According to reports, Mel B has slammed Victoria Beckham – who is said to have declined the invitation to take part in the celebrations.
Speaking to The Sun, an insider said: "Mel B has been telling friends that she is angry at Victoria for not getting in contact with her directly."
Victoria, 41, has hung up her microphone for good as she focuses on her growing high-end fashion line – but 39-year-old Mel is reportedly unimpressed with the 'snub'.
The source continued: "She was worried that it would put the tour's success in doubt because when they have reunited previously it's always been the five of them."
In an apparent dig at her former band mate, Mel committed the ultimate modern day friendship crime and unfollowed Victoria on Twitter – perhaps confirming their feud.
"Mel said that she thought Victoria was a snob for snubbing her bandmates and wanting to distance herself from her pop star past."
Earlier this month Geri Halliwell confirmed that there has been discussions over a possible reunion in 2016.