The 19-year-old underwent an MRI scan on Tuesday which confirmed the diagnosis that she would not be fit to compete.

The women’s 800m world champion, who had been expected to challenge for gold, only returned to competition in July after an 11-month absence from the sport following a series of gender tests.

South Africa Sports Confederation and Olympic Committee (SASCOC) chief executive Tubby Reddy stated that Semenya had told them in the last 48 hours she had been suffering serious lower back pain and had not been comfortable in her last few races.

He said: "Caster has had back pain for some time and continued to have pain after competing in a cross-country event at the weekend.

"Our doctor has since examined her.

"An MRI scan confirmed she has a back problem.

"We are satisfied that this is a bona fide injury.

"As such, SASCOC and Athletics South Africa agree that we are not in a position to compromise her health by risking her competing at New Delhi."

South Africa’s team doctor Shuaib Manjra added that if Semenya competed in Delhi, she risked serious injury blighting her chances at the 2011 Athletics World Championships and London’s 2012 Olympics.

Manjra said: "It would serve no purpose to have an athlete in Delhi who was struggling with any sort of injury that would compromise performance.

It is our medical view that physically and emotionally she would not be capable of doing justice to her talent at an event of this magnitude."

The news came after Semenya’s coach Michael Seme said she would be competing at the Commonwealth Games just yesterday morning.

He said: "She had a slight pain in the back, but the issue has been blown slightly out of proportion.

"She’s going to be 100 per cent fit.

"We are training and will be there."

Team South Africa, who have just moved into the Athletes’ Village in Delhi, are waiting on late fitness calls over long jump star Khotso Mokoena as well as men’s 800m world champion Mbulaeni Mulaudzi.

Mulaudzi is also feeling back pain and has undergone a last-minute scan to determine the extent of the problem while his manager Peet van Zyl fearing the worst.

He said: "With him not having trained for three weeks the outlook does not look good at all."

"The news is a further blow to the blighted event as with no Usain Bolt, Asafa Powell or Phillips Idowu, Semenya was set to be the major athletics attraction in Delhi.

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