After the little girl who lip-synched the song in the opening ceremony because she was prettier than the real vocalist, He Kexin was the story of the Beijing Olympics.

The tiny Chinese gymnast caused an international incident in August last year after rumours swept the internet that she was below the minimum age of 16 when she won gold medals for the uneven bars and the women’s team event.

The accusations of cheating levelled at China — mostly from the direction of America — exacerbated an already tense relationship between the host nation and the international media, forcing the International Olympic Committee (IOC) to order an official inquiry.

The subsequent investigation by the International Gymnastics Federation, the sport’s world governing body, concluded a year ago that there was no case to answer. Based on evidence that included passports, identity cards and official household registers submitted by the Chinese Gymnastics Association, it ruled that the five Chinese athletes in question were of the correct age.

Yet, as He returns to the global stage in London on Wednesday in search of a world title on the uneven bars, the controversy refuses to go away. Against a background of doubt about the tactics of a regime intent on toppling the US from the summit of the medals table, China still faces questions about whether it fielded under-age gymnasts at the 2000 Olympics.

The international federation’s disciplinary commission is investigating the cases of Dong Fangxiao and Yang Yun, who are suspected of being just 14 during the Sydney Games.

Again, the dynamics of Sino-American relations are in play. The Chinese women’s team were bronze medal-winners in Sydney, ahead of the US in fourth place, just as they beat their closest rivals into second place in Beijing. It was China’s first women’s team gold medal — one of nine won by the hosts out of an available 14. He also beat Nastia Liukin, the American, to the gold on the uneven bars on the tie-break rule. Britain’s Beth Tweddle came fourth behind Yang Yilin, one of four Chinese women competing at the World Championships this week.

If Dong and Yang are proved to have been under age at the Sydney Games, the IOC could strip them of their medals. No decision is expected before February but their case has re-opened the debate about age eligibility after the international federation declared it was not satisfied with the “contradictory documents” submitted by Chinese officials.

Similar conflicting evidence was available in the case of He. An American internet security consultant claimed last year that he had found documents on the web that showed He’s birthday as January 1, 1994, which would have made her 14 at the Beijing Games. Her date of birth, according to official accreditation, is January 1, 1992. But the international federation accepted explanations by Chinese officials that the discrepancies were the result of paperwork errors and inaccurate web entries.

Gymnastics insiders say the sport has moved on from the furore of Beijing and accepts the presence at the O2 Arena of the four female Chinese athletes — and their official ages of 17. “What can you do when documents are produced by a government?” said one. “No one wants to declare war on the Chinese.”

But the international federation has moved to tighten its rules in the wake of a damaging rumpus. It raised the minimum age from 14 to 15 in 1981, and again to 16 in 1997, precisely to protect young athletes from serious injury and exploitation by coaches.

From this week, it will be mandatory for any junior or senior gymnast competing in international competitions to hold a personal licence proving his or her age.

While it will still be based on a passport, meaning it will not prevent age manipulation through forged documents, it will at least provide some consistency by allowing the federation to track gymnasts through its system.

This should prevent a repeat of the case of Kim Gwang Suk, the Korean gold medal-winner on the uneven bars at the 1991 World Championships, who was later discovered to have been listed as 15 years old for three consecutive years.

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