Newlywed Ciara has accused her ex-fiance Future of costing her a lucrative $500,000 endorsement contract by bad-mouthing her in their ongoing legal battle.

The Goodies hitmaker is suing the rapper for $15 million amid allegations he knowingly made false and defamatory statements about her parenting skills on social media.

The lawsuit was filed in February (16), 17 months after Ciara initially dumped Future, the father of her young son, Future Zahir, who was born three months before the break-up.

The former couple has been firing shots at one another through legal papers ever since, and now Ciara is claiming the nasty dispute has cost her a big deal with an international cosmetics company.

In new legal papers obtained by TMZ.com, Ciara alleges Future's negative comments about his ex damaged her "positive reputation", making her out to be a bad mother, as well as sullying her as "controlling, dishonest, malicious, unreasonable, evil, (and) conniving".

The latest development in the defamation fight emerges weeks after Future revealed he was dropping his countersuit against Ciara, insisting he bears no ill will towards his ex-fiancee in a candid interview with Rolling Stone magazine.

"Ciara being successful, her being happy, helps me," Future said, before addressing the singer directly, adding, "I'm attached to you. If you're happy, I'm happy. You're connected for life. I don't want you to go through this... and for it to come back on my son, my kid. I want you to be in the best situation."

However, the singer didn't appear to be convinced as she then filed papers alleging she feared for the life of her then-fiance, football star Russell Wilson, as Future had reportedly threatened to cause him harm on social media and in song.

Ciara wed Russell days later, tying the knot in an English castle on 6 July (16).