Madonna has ended her friendship with Britney Spears, after the Toxic singer announced she was no longer studying Kabbalah, according to media reports in the US.

The Hung Up star had reportedly taken Spears under her wing and spent a great deal of time and money educating her about the mystical offshoot of Judaism.

Spears revealed she was quitting Kabbalah on her personal website, where she declared her new "religion" was caring for her son, Sean Preston.

According to The Scoop website, Madonna is also demanding Spears return a 12th century book on the religion she gave to the singer as a wedding gift.

A source says, "Madonna spent months teaching Britney the Kabbalah system, and splashed out thousands on the ancient scripture for her.

"She feels she has wasted time, money and precious gifts on Brit."

Spears, who was raised a Baptist, has allegedly been working with a "Christian life coach" to help her through recent emotional rough patches.