Mel B reveals one-night stand with bandmate Geri Halliwell

The Spice Girls at the height of their fame. Photo / News Corp Australia

Mel B has revealed she once slept with bandmate Geri Halliwell.

In news that will shock Spice Girl fans, Scary Spice said the pair enjoyed a night of passion, which they "giggled" about afterwards.

Mel joked that Geri, who is now married to Formula One boss Christian Horner and has two children, would "kill her" for talking about their intimate encounter, reports news.com.au.

The singer made the shock revelation as she spoke to Piers Morgan for his upcoming Life Stories series at a TV recording on Friday night.

Mel nodded after Good Morning Britain's Piers then asked: "Did you sleep with Geri like that?"

Brown said Ginger Spice Geri would be fuming at the raunchy revelations.

"She is going to hate me for this because she is all posh in a country house but it wasn't a thing – it just happened and we just giggled at it and that was it."

Geri Halliwell with husband Christian Horner. Photo / Getty Images

Piers Morgan described the statement as "a Spice Girls' bombshell".

"You have never admitted this before, have you? People are going to be fascinated," he said.

Mel answered: "Yeah, and I have said it now."

Brown said Halliwell "is going to kill me and so is her husband."

Brown told Piers Morgan she chose not to make the revelation in her book Brutally Honest because she said she wanted to focus on other aspects of her life.