The singer has been under legal conservatorship of her dad Jamie since her breakdown in 2008, and the phone ban is said to be just one of the measures taken by those close to her to avoid another.
A source told The Sun, 'Britney's inner-circle keep a close eye on her to ensure she keeps herself together.
'One of the rules is she gave up her cell phone. That helps them keep her under control.'
Her former bodyguard Fernando Flores, 30, claimed that the 29-year-old sent him nude pictures that she took of herself on her mobile and threatened to use them in a lawsuit. However, Britney denied the allegations.