Paula Radcliffe has revealed she has a low-grade stress fracture of her left femur but is “90-100 per cent likely” to compete in this summer’s Beijing Olympics.

Radcliffe, who missed last month’s Flora London Marathon with a toe injury, has been on crutches just 14 weeks before she bids to win the marathon in China.

This injury is just one of a number of setbacks she has had in recent times, with the hip problem having caused her considerable discomfort for some time.

An MRI scan did not pick up the problem, but a second test revealed that a muscle had pulled away and was putting pressure on her bone, with it now appearing that a more thorough scan has discovered the stress fracture to the thigh bone itself.

Four years ago in Athens, after suffering injury in her build-up to the Olympics, Radcliffe ended the race in tears, sitting on the side of the road after stopping three miles from the finish in the gruelling heat. Now she faces another race against time to be ready for China where, if fully fit, she would be Britain’s leading hope of a track and field gold medal.

Radcliffe, the marathon world record-holder, is one of the most stoic and biggest-hearted competitors in athletics. She has twice won the New York Marathon and the 2005 world title despite further injuries, and is determined to compete in what, at 34, is almost certain to be her last Olympics.

One of the biggest problems facing Radcliffe apart from the recovery time needed to come back from her current setback, is her lack of race fitness and what it will do to her training plans.

Radcliffe revealed she had been told by specialists it would now be “impossible” for her to complete enough training to be fully fit for Beijing. Although she admitted it was a “bombshell” to learn of the fracture, Radcliffe insisted: “It’s going to be tough but I’m not giving up.

“Everything has been with Beijing in mind, it’s been a huge focal point and it’s hugely important to me. It’s going to go down to the wire and I will need a bit of luck.

“It’s been a nightmare last three weeks but I’m trying to stay calm about it. “I’m thinking positive. I am looking at it as 90-100 per cent that I will be in Beijing, other people will put it a lot lower. I can do it.”

Radcliffe has competed only twice since the end of 2005, during which time she suffered injury and gave birth to her first child. Almost nine months after her daughter Isla was born, she finished second in the Bupa Great North Run last September before winning the ING New York Marathon in November.