It was never easy keeping up with the Joneses and yesterday the reason became clear. In one of the most seismic confessionals of a sport long tainted by liars and cheats, Marion Jones admitted she had taken steroids before her five-medal haul at the Olympic Games in Sydney in 2000. She faces up to six months in jail.

Many will not be surprised, given that Jones has long been a target for suspicion. Her former husband, C. J. Hunter, the shot putter and fellow cheat, claimed that she injected herself with human growth hormones, while Victor Conte, the founder of the Balco drugs factory, said she used performance-enhancing drugs “before, during and after the 2000 Olympics”.

Both are discredited figures, however, and Jones had always maintained her innocence, filing a $25 million (about £12.2 million) lawsuit against Conte in 2004 for his claims that he supplied her with drugs.

However, in an e-mail to family and friends that was published in the United States yesterday, Jones finally admitted she had been living a lie and had taken tetrahydrogestrinone, also known as THG and “the clear”. She attended the US District Court in New York yesterday to plead guilty to charges of having lied to federal agents about her doping and another matter relating to a counterfeit cheque. She arrived early in the afternoon and, after being processed, finger-printed and booked, admitted the charges before, minutes later, announcing her retirement. She was released and will return for sentencing on January 11.

“I lied because I panicked,” Jones wrote. “I lied to protect my coach at the time [Trevor Graham]. I lied to protect all that I had worked so very hard for in my life and career. And lastly, I lied to protect myself.

“It was an incredibly stupid thing to do. I made the decision to break the law and have to take full responsibility for doing so.” However, while admitting taking drugs, she said she had done so unknowingly and blamed Graham, who is due in court next month on charges of making false statements to federal investigators.

Jones claimed that in 1999, Graham advised her to take a “nutritional supplement” that he called flaxseed oil. “It was not until after I left Trevor at the end of 2002 that I began to wonder whether or not Trevor had given me something to enhance my performance,” she wrote. “Looking back in hindsight, red flags should have been raised in my head when he told me not to tell anyone about our workouts or supplementation program.” She agreed because she did not want to give her competitors any edge.

Jones wrote that the sentencing guideline for her offence is up to six months in jail, but the maximum term for lying to a federal agent is actually five years, suggesting that she has cut a deal with prosecutors.

Now 31, she is almost certain to be stripped of the gold medals she won in Sydney in the 100 metres, 200 metres and 4 x 400 metres, and the bronze medals in the long jump and 4 x 100 metres. An International Olympic Committee statement said it had an open file on Balco, the Californian company founded by Conte, and that Jones’s comments may prove “key in moving this case forward”.

Jones said she felt only shame as she announced her retirement last night. “I have let my fans down, I have let my country down and I have let myself down,” she added in a tearful address outside the court.

She was also charged with lying to investigators about a $25,000 cheque that was deposited in her account. The cheque was counterfeit and Jones denied any knowledge of it. Now she claims that Tim Montgomery, the disgraced sprinter and father of her child, gave it to her.

From being the golden girl of athletics, Jones is struggling to survive. Her relationships with Hunter, who was once found to have 1,000 times the normal level of nandrolone in his system, and Montgomery, whose world 100 metres record has been expunged, invited cynicism. The rush to condemn Jones last year, when she tested positive for erythropoietin, proved premature when the B sample cleared her, but the races had long dried up. Now married to Obadele Thompson, the former sprinter, she filed a breach-of-contract lawsuit in June that revealed she had savings of only £1,000. It is the riches-to-rags downfall that should serve as a cautionary tale for drug cheats the world over.