"Britney was the overwhelming choice" for worst celebrity dog owner for 2006, Hilary O'Hagan, editor of The New York Dog and The Hollywood Dog magazines, said in a statement.
"She once had three Chihuahuas ... and never left home without at least one of them on her arm," O'Hagan said. "As soon as she met K-Fed and had kids they (the dogs) disappeared."
Spears has filed for divorce from aspiring rapper Kevin Federline. The 25-year-old pop singer and Federline, 28, have a 1-year-old son, Sean Preston, and a 3-month-old son, Jayden James.
Paris Hilton, 2005's "worst" winner, placed second for "treating her dogs like accessories," the magazines said.
Winfrey, who owns five dogs, was voted this year's best celebrity dog owner. The talk-show host replaced 2005 winner Joss Stone, and beat off competition from Tori Spelling, Nicollette Sheridan and Beth Ostrosky, Howard Stern's girlfriend.
Voting took place online over a three-month period. Results weren't scientifically representative of the magazines' readers, and the total number of votes won't be released, O'Hagan said Monday.