WADA registered its appeal against the Court of Arbitration for Sport (CAS) verdict 12 hours after SIA did the same. 

Jack had her doping ban reduced to two years by the CAS in November, with the suspension backdated to July 12, 2019.

The Australian had originally been banned for four years after a sample she provided in an out-of-competition test in June 2019 was found to have contained ligandrol.

Jack's ban was reduced after the CAS confirmed she had committed an anti-doping rule violation, but the sole arbitrator found she "did not intentionally ingest ligandrol and considered that she had discharged her onus of proving that the anti-doping rule violation was not intentional".

It is understood WADA feels the reduction of the four-year ban is too lenient, as reported by ABC. 

WADA Executive Board member Dick Pound had been bullish following the CAS decision to reduce the suspension.

"Your athlete was not innocent - it was a doped athlete, it was a doping offence," he said.  

"The only argument was the length of the sanction? 

"She got that reduced because the CAS panel determined there was no significant fault.

"I don't know what evidence they heard to overturn the four-year part, as opposed to two years, but that's what courts are for... the sentence of the guilty person is reduced, but the person is still guilty." 

This was after the anti-doping system received criticism from figures such as United States Anti-Doping Agency chief executive Travis Tygart and Australian swimmer Cate Campbell.  

The SIA said it had appealed the CAS decision "on the need for clarity in the application of key anti-doping legal principles".

Swimming Australia and the International Swimming Federation can still also appeal the decision. 

Jack, who had claimed cross-contamination could have caused her positive drugs test for the non-steroid anabolic agent, had responded to the CAS ruling with a statement posted on social media. 

The 22-year-old, a member of Australia's 4x100 metres freestyle team that won gold at the Gold Coast 2018 Commonwealth Games, said she accepted the decision "with a positive attitude and with gratitude that my career as a swimmer will resume next year".

It is unlikely she will be able to return to swimming as soon as she had planned, however, with the appeal process expected to last from six to nine months. 

The Swiss Federal Tribunal is the only place where CAS verdicts can be appealed.