The World Anti-Doping Agency has come under fire for taking five years to begin investigating allegations of systematic doping in China that were first made by a whistleblower in 2012.

On Sunday the Chinese doctor Xue Yinxian told the German broadcaster ARD that more than 10,000 Chinese athletes had used banned substances during the 1980s and 90s, including every medal winner in every major championships – claims that Wada has now referred to its intelligence unit for scrutiny.

However, Wada’s critics have pointed out that Xue, whose elite roles included chief medical supervisor for the Chinese gymnastics team, made similar claims in an interview to the Sydney Morning Herald in 2012, where she described doping in China as “rampant in the 1980s” and said that anyone who rejected drugs “would face punishment or criticism”.

The 79-year-old, who is seeking political asylum in Germany, also told the paper that she had fought a losing battle against systematic doping in elite sport in China, although she did not mention how many athletes she believed had doped.

Renee-Anne Shirley, the former head of Jamaica Anti-Doping Commission, wrote on Twitter: “Dr Xue made these accusations in 2012 but Wada did nothing about them then. Guess they only move when ARD TV does a documentary?”

Shirley also criticised the International Association of Athletics Federations, for what she called its “wimpy” response to a letter published in February from Chinese athletes linked to the controversial track coach Ma Junren, whose athletes broke 66 national and world records, which said they had been forced to take performance-enhancing drugs.

In response to Shirley’s claims, Wada pointed out that it was only formed in November 1999; and, only in January 2015, acquired the power to investigate under the 2015 Code. “Since then, the agency has built up its intelligence and investigations capability and exercised this power as appropriate,” a spokesperson told the Guardian.

“The same applies here – the agency will ensure that, if action is warranted and feasible under the Code, all the necessary and appropriate steps will be taken.” Wada also confirmed it would be willing to work “with or alongside” other anti‑doping bodies, including the IAAF’s Athletics Integrity Unit, to get to the truth of the matter.

Xue, who was dismissed from the Chinese national team for refusing to give a young gymnast a banned substance at the 1988 Olympics in Seoul, has said that children as young as 11 were taking banned drugs to improve their performance and that the state-run doping system covered every sport from athletics to weightlifting.

She has also called for “all international medals” won by her country during that period should be declared void because they are “tainted by doping – gold, silver and bronze. “There must have been more than 10,000 people involved. People believed only in doping, anyone who took doping substances was seen to be defending the country,” she added.

However the chances of any convictions are slim given the difficulty in prosecuting cases decades after the alleged offences.

The International Olympic Committee confirmed it was aware of Wada’s investigation into the claims. A spokesperson said: “The World Anti-Doping Agency is looking into the allegations – this is their role.”