The 31-year-old 'Whole Again' singer, who reunited with Kerry Katona and Liz McClarnon for the show last year, vented her disappointment on Twitter last night.
It was announced on Thursday that the male groups from series one and two would be going on an ultimate boy band tour in October.
5ive, Blue, 911, A1, 3T, 5th Story and Damage will be on the road for the 13-date tour, but it will not feature any of the girl groups that have participated in the show so far.
This means fans will not get to see last year's stars Atomic Kitten and Honeyz, or Eternal and Girl Thing from this year's show.
Natasha said: "@BigReunionITV boys tour only? Feeling very bad for the ladies of this years show, don't even get a look in. Nice to see equality 4 all."
Natasha, who is dating fellow Big Reunion star and 5ive member Ritchie Neville, said she wouldn't let the announcement upset her.
The mum-of-three added: "But not gonna let anything get in my way today, it's international happiness day:) & u know what, I couldn't be happier right now #blessed x."
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Watch the trailer for the 'Boy Band Tour' below: