Mel actually missed the first night of the final shows after arguing with her ex, after he accused her of sleeping with her fellow judge The Sun reports.
She was hospitalised following the fight and appeared on the show the next day with bruises on her body.
"Stephen’s jealousy at that point was causing massive problems in the marriage – and he was convinced something was going on between her and Simon," a source reveals to the publication.
"He did not like the fact Mel obviously looked up to him and spoke about him a lot.
"He thought she was up to all sorts at the time – but accusing her of sleeping with Simon was a real low point.
"He just couldn’t control his jealousy and anger when she was appearing on such a high-profile show with successful people that he didn’t know.
"It caused huge arguments and led to a loss of trust that never really healed.
"It is definitely one of the things that led to the eventual breakdown of their relationship."
Yesterday an X-Factor source said: "Belafonte is an odious character who will say anything – and these claims by him are laughable.
"There is no truth in the accusations that anything happened between Mel and Simon.
"They don’t even have a flirty relationship.
"Simon likes her, and thinks she is professional, so looks out for her as a friend."
Well, that's that then.
Our fave Spice Girl is currently in the process of filing for divorce from Stephen after 10-years of marriage and has won a restraining order against him amid claims of physical and emotional abuse during their marriage.
If you, or anyone you know are experience domestic violence or abuse, please contact Lifeline on 13 11 14 or visit their site.