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Dismayed by a reality-TV show featuring his ex-fiancee, Bristol Palin, and their son, Tripp, Levi Johnston plans to seek full custody of the boy.

In a statement to ABC News, Johnston wrote, "I want full or half custody of Tripp. His room is already set up in my house and just waiting for him."

Palin, 21, and 3-year-old Tripp are featured on the Lifetime show, "Bristol Palin: Life's a Tripp." Johnston says the show is proof that his ex is a terrible parent and his son is "on a downward spiral," the gossip website TMZ reported.

TMZ reported that Johnston, 22, is so "disgusted" by his son's language and behavior that he obtained the required court papers to file the custody petition.

"I love my son more than anything … and I will do whatever it takes to make sure he is raised the right way," Johnston reportedly told TMZ.

In a recent episode of the show, Tripp threw a temper tantrum when told he couldn't go to the pool. When his aunt, Willow, tried to calm him, Tripp told her and his mother that he hated them, then told Willow, "Go away, you f***!"

Initial reports indicated Tripp had used an anti-gay slur, but his mother said in a blog post that he "used a different 'f word.'" Palin confessed on the show to doing "a terrible job disciplining Tripp."

Of her son's behavior, she also wrote that the cameras "caught a moment on film that would cause any parent to be red in the face."

Johnston was Palin's high school boyfriend. The pair have been engaged twice but are no longer a couple.

Under the terms of their child-custody agreement, Palin has primary custody and Johnston may visit Tripp.

The agreement prohibits either parent from publicly disparaging the other.

Since the pair split, she has been a spokeswoman for teen abstinence, written a book and appeared on ABC's "Dancing With the Stars." Johnston has posed for Playgirl magazine and written a tell-all book about his relationship with Palin and the Palin family.

Palin is the daughter of former Alaska governor and one-time Republican vice presidential candidate Sarah Palin.

The disclosure during her mother's 2008 campaign that Bristol Palin, then 17, was pregnant created sweeping controversy.