Jimmy Gulzar has a question for Mel B -- if Stephen Belafonte is as bad as you say he is ... why did you let our daughter live with him all these years?

Mel's ex-husband blasts her for failing as a mom to keep their 18-year-old daughter, Phoenix, out of harm's way with Belafonte. He says he's known for years Stephen had a gun which he's not allowed to own, and claims it's another example of Mel's poor parenting.

Jimmy's already told us Mel B has gone to great lengths to keep him from seeing his daughter, but he's placing blame on many others for not helping Phoenix ... and dismissing claims he's just an "angry ex."