The 39-year-old X Factor judge and Stephen, 40, got married in 2007, but seven years later Mel insists they're still going strong.
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Mum-of-three Mel's Spice Girls band mate Emma Bunton was recently in Mexico with her for the judge's houses round, and she used her as an example of how to have a successful relationship.
Speaking to the Mirror, she said: "You know Emma and Jade [Jones, of Damage] have been together for 15 years and do you know what she's wearing under there? Leather!
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"They are friends and they still fancy each other and love each other. That's the key to any successful relationship. You get on, you argue, you love each other.
"I laugh at Stephen a lot. He's a loud American sometimes, but he's great. I bought him an island for his birthday – it's secretly as much for me too, though."
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Scary Spice also revealed a slightly unusual way of making her relationship work: she has regular bitching session about Stephen with a therapist.
She said: "I have therapy and I like it. Usually I bitch and moan about my husband. Silly things like he likes to sleep with the TV on but it keeps me awake.
"There is a debate every night. He ends up winning because he puts something on that I actually want to watch."
But Mel hit back at claims from her family that Stephen's 'controlling' ways has caused a rift between them.
Her sister Danielle once said that Stephen is 'controlling and not a nice person', and her dad Martin said her marriage was a 'strange relationship'.
Commenting on this, Mel simply insisted: "My husband let's me get on with whatever I want to do."