Mel B, Geri Horner and Emma Bunton were due to reunite this year to celebrate the girls’ 20th anniversary.
However, the reported move by Posh Spice has left their plans up in the air.
A source told The Sun: “The girls are devastated. It is an extremely sad way for things to end.”
Last year, the fashion designer said she preferred if the trio sang their own material.
Speaking to Claudia Winkleman, she shared: “I do think they should sing their own material though, because what we did in the Spice Girls was so special. If they sang Spice Girls songs I think I might be a bit sad.”
A source added to the newspaper: “Victoria is proud of her Spice Girls history but this suggests she wants to cut all links with the group which transformed her life.
“She is resorting to aggressive legal letters and it is an extremely sad way for things to end after all they have been through together.”