Scary Spice Mel B hinted on Australian television that the girl group will reform for a one-off gig at Buckingham Palace on June 4.
Asked on breakfast show Sunrise if the Spice Girls will perform at the 2012 Olympics opening ceremony, Mel B replied: "Well, we do have the Queen's Diamond Jubilee coming up. Did I really say that?"
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The singer then changed the subject after realising she had let the news slip, but confirmed the plans to studio workers, The Sun reports.
"I am going to be in such strife for saying that. It's all so totally bloody top-secret still," she apparently said.
Mel B also said on the Seven Network morning programme: "I'm always down for a Spice Girls reunion. For me to get my Scary hair on and my big platforms... [I'd do it] any time of day... I'm a Spice Girl through and through."
Tickets for the concert will be available to the public through a ballot system and the gig will be broadcast on TV.
Mel B has previously hinted that the Spice Girls could perform at this year's London 2012 Olympics.
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Watch Mel B discuss the Queen's Diamond Jubilee Spice Girls reunion below: