Johnston and Bristol Palin were allowed to share a room in the Palins' Alaska estate with no interference from the lipstick-wearing pitbull or dad Todd Palin, Johnston said in an interview that will air on "The Tyra Banks Show" Monday, Us magazine reported.
"I'm sure she probably knew," Johnston said. "Moms are pretty smart."
The governor responded to Johnston's claims with a terse statement that said the jock was on "a quest for fame," according to Poeple.com.
"Bristol did not even know Levi was going on the show. We're disappointed that Levi and his family, in a quest for fame, attention, and fortune, are engaging in flat-out lies, gross exaggeration, and even distortion of their relationship," the statement from the Palin family said.
"Bristol's focus will remain on raising Tripp, completing her education, and advocating abstinence. It is unfortunate that Levi finds it more appealing to exploit his previous relationship with Bristol than to contribute to the well being of the child," the statement said. "Bristol realizes now that she made a mistake in her relationship and is the one taking responsibility for their actions."
Johnston also revealed that he and Bristol didn't always use protection - they only practiced safe sex "most of the time," Johnston said.
Palin, 18, gave birth to son Tripp Easton Mitchell on Dec. 27. News of the teen's pregnancy broke during Sarah Palin's vice-presidential campaign and quickly became a public relations nightmare for the conservative candidate.
The couple broke off their engagement in March and remain friends, Johnston said last month.