Mel B Says Not Everyone in Spice Girls is 'Honest' Enough for a Documentary

Don't expect to get a Spice Girls documentary anytime soon ... at least not according to Mel B!

This year will mark the 30th anniversary of the girl group's debut -- their first single and album both dropped in 1996 -- but Mel is shutting down rumors that she'll reunite with Victoria Beckham, Melanie C, Geri Halliwell and Emma Bunton for a doc.

She told Hello it's not that they haven't been asked or weren't considering it, but she's not sure it would get done "in the right way," saying ... "It has to be honest -- and not everybody wants to be honest."

Scary Spice didn't name names ... but she did squash any hope for a reunion tour, stressing "it's not happening."

She said ... "If it does, it’ll be a shock to me, let’s put it that way."

Mel explained she doesn't want to be "nagging" the girls about getting the group back together, noting ... "I laid that to rest when I turned 50."

She's not even sure that she'd be interested, adding ... "I’ve got fond memories, but I don’t know if I would want to go back up on stage."