The couple's former nanny claims:
1. Mel B acted 'as a cameraman' to film threesomes.
2. Alleges she had sex with former Spice Girl 'multiple times' a week.
3. Says the couple has footage of threesomes which she is terrified will be leaked.
Mel B, 42, filed for a divorce from Belafonte, 42, in March claiming that Gilles had an affair with her husband of 10 years and also had an abortion.
But now with the dossier she has hit back at the singer who also claimed that Belafonte abused her during their marriage.
The married 26-year-old German babysitter says that the couple have footage of their threesomes on their mobiles and that she is scared they will be leaked online.
"These recordings would be extremely embarrassing to me and my family… I do not want any of them to become public," she wrote in the lawsuit.
In the document Gilles also claims that she became embroiled in a sex triangle with the high profile couple.
She states in the papers: "My sexual and employment relationship with Melanie continued for approximately seven years until September 2016.
"During my time with Melanie, she and I had sex sporadically, sometimes having sex multiple times in a week.
"On the other hand I never had any sexual relations with Stephen without Melanie's instruction and without Melanie's actual or apparent consent. At no point did I represent to Melanie that I was pregnant with Stephen's child.
"The only times Stephen and I had sex was when Melanie instructed Stephen and I to do so.
"Or when Melanie herself invited her husband to join us in the bedroom, at which point Melanie would often serve as the 'camera man' and record the sexual encounter or take part in the menage a trois herself."
The America's Got Talent judge has accused music producer Belafonte and Gilles of taking money from her.
Gilles admitted she told Mel B she was excited to share a sex act with the singer at the weekend, adding in the explicit email: 'It has been too long!'
In the dossier filed by her legal team with California's Superior Court on Friday, Gilles hit back after Mel portrayed her as a 'home- wrecker'.
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