Madonna kicked off her Sticky & Sweet Tour in the U.K. Saturday, and stirred up a beehive of controversy by comparing Republican presidential nominee John McCain to Adolf Hitler in a video montage during the show.

During the song "Get Stupid," Madonna flashed images of McCain alongside photos of Hitler and brutal Zimbabwean President Robert Mugabe, as well as images of destruction and global warming, according to British paper The Times.

By contrast, in the next segment of the performance, she used the image of Democratic nominee Barack Obama alongside pictures of John Lennon, Mahatma Ghandi and Al Gore.

McCain spokesperson Tucker Bounds for was quick to respond to the slam, and pursued the Obama-as-celebrity tack the campaign has employed in recent weeks.

"The comparisons are outrageous, unacceptable and crudely divisive all at the same time," he said. "It clearly shows that when it comes to supporting Barack Obama, his fellow worldwide celebrities refuse to consider any smear or attack off limits."

Tommy Vetor, a spokesperson for Obama's camp, also spoke out about Madonna's controversial move. "These comparisons are outrageous and offensive and have no place in the political process," he said in a statement to CNN. "We hope that John McCain will offer a similar condemnation as his allies increasingly practice sleazy swift-boat politics."

Last month, McCain's campaign released an ad criticizing Obama by comparing him to celebrities like Britney Spears and Paris Hilton. Hilton then made a video spoof where she declared she'll be running for office.

Madonna, on the other hand, has courted controversy with every tour, most recently with her Confessions trek in 2006, which included a mock crucifixion that drew criticism from the Vatican, among others.

The Sticky & Sweet Tour continues through Europe until the end of next month, and premieres in the U.S. on October 4 in New Jersey. On Election Day (November 4), Madonna is slated to perform in San Diego.