Birkhead, who was proven to be the biological father of Smith's daughter, said he decided to buy four items of Smith's lingerie collection at the Planet Hollywood Resort auction as a future gift for their daughter, the Las Vegas Review-Journal reported Sunday.
"I've got a big puzzle to put together for her," he said of their 1-year-old daughter.
Birkhead told the Review-Journal his purchases at Saturday's celebrity auction by Julien's Auctions actually went again a sales plan he had been considering.
"The irony is I was considering doing an auction of all the overflow (memorabilia)," he told the newspaper.
Celebrity Couples of 2014 [PHOTOS]