The day before ABC announced it was doing an American version of the hit U.K. family behavior makeover reality show “Supernanny,” Fox bought “Nanny 911,” a reality series with a remarkably similar premise.

“Supernanny” stars Jo Frost, a veteran British nanny who moves in with a family and offers parents tips on how to better raise their children. The show will follow up with the family and see whether Ms. Frost’s suggestions have made a noticeable difference. Nick Powell, who created and executive produced the original for Ricochet Ltd., is on board for the American version.

ABC announced Wednesday it was immediately going into production on the eight-episode series. Fox, which made its own pitch to buy “Supernanny,” bought “Nanny 911,” from U.K. production company Granada. A Fox spokesperson said the network closed the deal with Granada Wednesday and had bought the idea in the room the night before.

“Nanny 911” will feature a stable of nannies, with one being chosen each week to deal with a different family looking for some parenting direction.

The dueling nanny-based shows are the latest development in the Fox-ABC reality show rivalry. ABC charges Fox rushed the production and summer premiere of “Trading Spouses: Meet Your New Mommy” to weaken its family-trading show “Wife Swap,” which begins airing in the fall.