The '4 Minutes' singer - who is currently rehearsing for her forthcoming world tour - has reportedly fired two dancers, while her tour manager is allegedly threatening to quit due to her "spectacular mood" swings.

Madonna has been rocked by claims her marriage to Guy Ritchie is on the rocks and by allegations she is having an affair with baseball star Alex Rodriguez. Her brother Christopher released a tell-all book about her last week, which is said to have devastated her.

A source close to the singer revealed to Britain's The Sun newspaper: "Madonna is doing less than OK. She has been rehearsing for the tour and she is totally miserable. "She's down physically and mentally.

The situation with Guy is very, very tense. The way everyone is going crazy with the A-Rod story, her brother's book and her physical exhaustion are all taking their toll. "She feels nobody has taken her side. One of her closest pals says she has never seen Madonna so low.

She has been feeling down and looking really gaunt." As Madonna struggles to cope with the stress, she has been diagnosed as anaemic and the usually super-fit star has suffered a knee injury.

Following her knee injury, doctors have ordered the 49-year-old to take a break and she is reportedly staying with close friend Gwyneth Paltrow at the Hamptons resort in New York. Medics have advised she lessens the strain of her dance routines when she does return to rehearsals.

The source added: "Madonna was told to go soft on work and rehearsals, so she will now take one proper day off every week and go easy in the mornings. "She has a blood analysis done every few days - including one during last week's rehearsal in front of everyone."