Madonna is not afraid to offend people of faith with productions such as her 1989 Like a Prayer video, which featured burning crosses, stigmata and steamy kissing session with a black saint, drawing condemnation from the Vatican.

Now she's fallen foul of America's Catholic League for a number on her Rebel Heart tour at Madison Square Garden in New York. Her song Holy Water saw her strip off her skirt to reveal a skimpy nun's habit costume as she held a pole in the shape of a crucifix. Other dancers were also dressed as nuns.

Catholic commentator Bill Donoghue attacked her "mockery of the Catholic religion". "Madonna ages, but she never changes," he said, adding: "Examples of Madonna's anti-Catholic performances over the years abound."

"Now, at age 57, these seem to have become her last refuge as she struggles to avoid becoming an entertainment has-been," he said. "For her and her fans, apparently, Catholic-bashing is the one thing that never gets old."

Madonna practises the Jewish Kabbalah system. In a Harper's Bazaar interview last year, she admitted that while she is a "big believer in ritualistic behaviour as long as it doesn't hurt anybody", she is "not a huge fan of rules".

"I have a funny relationship with religion," she said at the time.

Speaking last year to illusionist David Blaine for Interview Mag she said she sets aside time for prayer. But for her it's more a process of giving thanks, than making a spiritual connection with a deity.

"The ritual of prayer isn't a religious thing as much as it is having a ritualistic moment to acknowledge things and not take things for granted," she said.

"For instance: the fact that you wake up and there's air in your lungs; the fact that you have a job to do; the fact that you have friends; the fact that you have your health. You're going to do something that's going to bring you joy. We take these things for granted. And, you know, I think it's important to call angels to you to protect you."