The former Spice Girls signer filed for divorce from the TV producer last month and obtained a restraining order after accusing him of abusing her, getting their nanny pregnant and forcing her to take part in threesomes.
And it has now been claimed the 57-year-old music mogul - who has worked alongside Mel for several years on 'The X Factor' in the UK and 'America's Got Talent' - gave his friend the push she needed to walk away from the relationship.
According to TMZ, Simon and others working on the shows felt there was something ''seriously wrong'' with the marriage, but Mel, 41, would never admit to anything and made various excuses to explain away her bruises.
However, the Syco boss eventually ''stepped up'' to warn Mel her husband was a ''bad guy'' and ''bad news'' and encouraged her to leave.
And the insider claims the 'Viva Forever' singer - who has five-year-old daughter Madison with Stephen, and Phoenix, 18, and Angel, 10, from previous relationships - is giving Simon part of the credit for her finally calling time on her 10-year marriage.
The 'Britain's Got Talent' judge recently praised Mel for ending her marriage.
He said: ''She's an incredible person.
''If you think about what Mel's done since leaving the Spice Girls and what she's gone through, how hard she works and how I saw her try to handle this situation, it was astonishing.
''I think she is a really, really special person, and I really respect the way she's dealt with everything.
''Yes, she's under pressure but I think she's in a good place.''
It was previously claimed Simon had helped Mel get in touch with a divorce lawyer after she tried to overdose on Aspirin due to stress before 'The X Factor's live finale in 2014.
A source said: ''Although no-one was sure what was going on, Simon and the team at Syco really became concerned at 'The X Factor' finale in 2014.
''In the days afterwards, following her release from hospital, they tried to help her leave Belafonte. They introduced her to divorce lawyers to help her to go through with it.''
A Syco spokesperson added: ''Melanie is hugely admired and respected by everyone at Syco and on both 'The X Factor' and 'America's Got Talent'.
''We have always supported her whenever she has requested and we will continue to do so.''
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