The former EastEnders actress's ex-fiancé Adam Cottrell was previously sentenced after pleading guilty to attacking her at her Hertfordshire home in April.
Following Hageman's win on Simon Cowell's new ITV1 gameshow, it was revealed that the bricklayer had spent two and a half years behind bars for actual bodily harm.
"Reading about that brute Nathan Hageman left me feeling sick to the stomach – men who commit crimes like that should feel the full force of the law, not bag themselves a million on a game show," Cassidy wrote in The Mirror. "The issue at the heart of this really shouldn't be brushed under the carpet by the TV show – especially now that the shocking details of his crime have come to light."
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Of the incident between Hageman and Amy Edwards, Cassidy continued: "I'm incredibly lucky that the physical attacks I went through were nothing like as vicious as that - much of the abuse I suffered was emotional, although there were incidents of violence.
"But just the thought of being at home on a Saturday and seeing him appear on TV, hugging Ant and Dec and being handed a million pounds, leaves me furious. The poor girl who was victimised by this man was promised that justice would be done – he was sentenced to five years in prison but only served half of it."
The 28-year-old said that Edwards "must be absolutely furious" and criticised the checks which failed to find out the "specifics of any convictions".
Cassidy added: "I've worried about it myself in the past. I fear that a reality TV show or chat programme might invite Adam to take part and talk about our relationship.
"Seeing him on my living room TV while I'm sitting with my family would be absolutely unbearable and I'm sure the young girl involved in this crime feels exactly the same."
Red or Black? continues tonight at 8pm on ITV1.
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Watch Nathan Hageman win on Red or Black?: