After Johnston, 19, claimed on CBS' Early Show Wednesday that Palin would often refer to her son with Down Syndrome, Trig Palin, as "retarded," the ex-governor fired back.
In a statement issued by her spokesperson, the Palin, 45, said she had tried to ignore the "mean spirited, malicious and untrue attacks on our family" but felt forced to respond.
"We, like many, are appalled at the inflammatory statements being made or implied," she continued. "Trig is our ‘blessed little angel’ who knows it and is lovingly called that every day of his life. Even the thought that anyone would refer to Trig by any disparaging name is sickening and sad."
Palin and Johnston -- who had a child, Tripp, with Palin’s daughter, Bristol, 19 -- have been in a war of words since the teen couple split earlier this year.
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His latest allegation against Palin comes two days after he told Usmagazine.com that he planned to appear fully nude for his upcoming Playgirl photo shoot. ("I just get naked," he told Us. "That's what I do.")
Palin, who believes Johnston is only speaking out to get "attention," also attacks the CBS network for broadcasting his lies.
"CBS should be ashamed for continually providing a forum to propagate lies," she said. "Consider the source of the most recent attention-getting lies -- those who would sell their body for money reflect a desperate need for attention and are likely to say and do anything for even more attention."