Valieva tested positive for the banned substance trimetazidine at the Russian national championships in December 2021 and the result was only made known on Feb. 8, a day after she helped her team win a gold medal at the Beijing Olympics.

Last month RUSADA said it would not release the results of the investigation into Valieva's positive test "in order to protect the interests" of the 16-year-old skater.

"Despite putting RUSADA under formal notice to resolve the Kamila Valieva case promptly, no progress was made. Therefore, I can confirm WADA has now officially referred it directly to the Court of Arbitration for Sport," Banka wrote on Twitter.

WADA had issued a "formal notice" to RUSADA last month after raising concerns with the ongoing delay in Valieva's case, warning the agency they would take the matter directly to CAS, which is sport's highest court.

In her defence, Valieva said the positive test was the result of a mix-up with her grandfather's heart medication.

CAS had cleared Valieva, then 15, to continue competing at the Beijing Games in February, upholding an earlier decision by RUSADA to lift a ban on the skater.

CAS had cited the fact that Valieva was a "protected person" under WADA rules as one of the "exceptional circumstances" underpinning its decision. The CAS ruling did not address the merits of Valieva's drug case.

At the time, WADA was disappointed with the decision and Banka had said, "doping of children is evil and unforgivable".