Brown poked fun at Beckham this year for Halloween, dressing as her bandmate alongside a lookalike of soccer star husband David Beckham with a sign reading: "No I am not going on tour".
The Spice Girls will kick off their United Kingdom stadium tour in June next year in Manchester.
The fashion designer has chosen to focus on her business and not partake in the highly-anticipated tour.
Victoria Beckham (Posh Spice) will not be joining the girls on tour.
"Victoria please, your fans need you on tour", a third added. She also shared a throwback photo of herself as Baby Spice on Instagram, writing: "Let's get this party started @spicegirls".
While the "Viva Forever" singer is confident the tour will be well-received, she admitted some of her bandmates were more cautious.
Though the group will unveil United Kingdom tour dates in a few hours time, Mel admitted they are hoping to take the shows global. Since that time, they have been frequently reassuring fans that a reunion is happening.
"We are absolutely thrilled that the Spice Girls have chosen our club to play a part in this very special reunion tour".
All the concerts will take place in June next year, with dates in Manchester, Coventry, Sunderland, Edinburgh, Bristol and London (Wembley). "X vb #spicegirls #friendshipneverends". Check out the Spice Girls' UK dates below.
Speaking on UK TV show "Loose Women", she said: "It's just the four of us, but she might join us at some point".
'I hope so, it'll be a shame if she didn't [come to the shows],' she continued.
Jess Glynne will be supporting them on the road - with tickets on sale on Saturday, 10 November.