London, Feb 5: Singer Britney Spears has been reportedly suffering from panic attacks as she prepares for her world tour `Circus'.

Apparently, the 27-old-year comeback queen has been throwing tantrums and locking herself in her room amid "terrible attacks of nerves".

According to the Sun, the singer's condition has become so bad that her father, Jamie, has had to call the doctor.

A source told the 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 will start her world tour next month and will be joined by sons Sean Preston, three, and Jayden James, two, reports the Telegraph.

Following her public meltdowns a year ago, Britney has remained under the strict control of her father, who has restricted her friends and regulated her medical treatment.

She starts in New Orleans on March 3 and ends with eight dates in London ending on June 14. (ANI)