It was announced last month that the blood-boosting substance erythropoietin (EPO) had been found in the A sample of Jones's urine test taken at the United States Championships in June where she won the 100m. But the back-up sample came back negative, leaving her free to continue competing. However, the American withdrew from the rest of the season blaming stress-related exhaustion.

"It's been a rollercoaster," she said in an interview published in the New York Times yesterday. "I'm not superhuman. All this weighs on a person and this has weighed on me too much. When I heard the news about the positive drug test, I said 'what else can I do? Maybe I should consider just not being in the sport.' The last five weeks have been the most difficult I've ever had to face. The stress level, the emotional toll has gone to a new stratosphere."

The 30-year-old sprinter has been dogged by allegations for more than three years since being linked with the Bay Area Laboratory Co-Operative (Balco). Among those who claim to have seen her use drugs is CJ Hunter, her former husband and the 1999 world shot put champion, who was suspended six years ago after testing positive for record levels of the anabolic steroid nandrolone. He alleged he injected her before the 2000 Olympics in Sydney where she won a record five medals, including three gold. She has denied the allegation.

Jones has been linked to several other figures implicated in doping. Tim Montgomery, the former world 100m record holder and father of her son, was banned in 2005 for two years following evidence uncovered during the Balco scandal.

She was also previously coached by Trevor Graham, a Jamaican who has had 13 athletes linked to doping, and Charlie Francis, who coached Ben Johnson during his career and has admitted giving the Canadian anabolic steroids.

"I've defended myself against this," said Jones. "I said I never used performance-enhancing drugs. I'm for a drug-free sport. This is the final straw. This is what I stood up for and fought for." Among those trying to talk Jones out of retiring is her family. "I came home and my family said 'you have got to fight,' so I go back and forth," she said.

"The last five weeks have been an eye-opener to me. The last five weeks made me realise that you have to be prepared for the next stage of your life - whether it is now or two years from now. I love the sport, I have a passion for it; Competing against the other women. But the rest of it is getting too heavy."

There will always be people who doubt and suspect. When I can't run any more, even if I run until I'm in my forties and retire, even then people will say, 'we finally got her out of the sport.'

"What weighs more is how the people who care for me are affected. How it weighs on them. People don't realise how other people are affected. My brother called me at 2am crying when the B sample came back negative. So it's not just about me, it's about all the people who have been there for me. It's tough either way. This has been such a major part of you. It's a life decision."