Mel B brought a scary level of spice to Mel C's recent show ... jumping onstage to perform a beloved Spice Girls song with her pal!

Sporty Spice -- who released her album "Sweat" on Friday -- had a show in Leeds Saturday night ... and she brought out her former bandmate, a native of the area.

Mel B showered praise on her pal ... saying she really enjoyed the performance to that point ... before playing "Spice Up Your Life" with her friend.

The two bounced around the stage to the hit ... singing their hearts out and getting the crowd rollicking.

It's the first time the Mels have been onstage together since the last Spice Girls tour -- which featured everyone from the group except Victoria Beckham.

While it's a nice moment for the two ladies, a full-on Spice Girls reunion is still up in the air ... with Mel B recently shooting down the idea.

Remember, she told Hello! last month that she wasn't going to badger the other girls into getting the band back together ... adding she'd be surprised if it happened.

Mel C, on the other hand, said last week that she hopes another reunion will happen ... so these two seemingly do want to grab the girls and hit the road again.

Last time all five members of the group performed together at a major event was the 2012 Summer Olympics in London ... though they did have a small reunion at Beckham's 50th birthday in 2024.

Bottom line ... we'll just have to wait and see if the ladies want to spice up the stage together again!