Britney Spears is suffering from anxiety ahead of the start of her world tour, it's been reported.

The singer is experienced a number of panic attacks during rehearsals for the tour, which gets underway next month.

Her concerned father, Jamie, is said to have called doctors over the singer's “terrible attacks of nerves”.

A source told the Sun newspaper: "Britney is in danger of not going on tour. She's been telling her doctor she's under pressure. She fears her performance will be branded a flop.”

Spears is planning to be take her two children, Jayden James and Sean Preston, on tour with her.

As previously reported, Spears' tour will include an eight night residency at London's O2 Arena.

(by Jason Gregory)