Ex-world number one Maria Sharapova, 29, had a two-year ban reduced to 15 months after the Court of Arbitration for Sport (Cas) ruled she was not told about a change in the drug's status.

She tested positive for meldonium less than a month after it was banned.

The ITF said "appropriate steps were taken to publicise any changes".

But, in a statement, it added: "Nonetheless, we have reviewed, and will continue to review, our processes for communicating changes to the prohibited list to players with the aim of ensuring that no player can claim that they had not been fully informed."

Sharapova is a five-time Grand Slam winner and was Forbes' highest-paid female athlete for 11 consecutive years, until American Serena Williams moved above her this year.

The Russian, whose suspension is backdated to the date of her first positive test on 26 January 2016, can return to action on 26 April 2017.

"I have learned from this, and I hope the ITF has as well," she said.

Sharapova tested positive for meldonium at the Australian Open in January 2016 and an out-of-competition test on 2 February.

She said she had been taking the drug since 2006 for health reasons and was unaware it had been added to World Anti-Doping Agency's (Wada) banned list as she knew it only by the name mildronate.

However, the Cas appeal hearing said Sharapova was at fault for not giving her agent "adequate instructions" in checking Wada's prohibited list and "failing to supervise and control" her agent.

Sharapova's lawyer, John Haggerty, called the Cas decision "a stunning repudiation of the ITF" and that "it exposes the ITF decision for what it is - pure fiction".

"As we demonstrated before Cas, not only did the tennis anti-doping authorities fail to properly warn Maria, if you compare what the ITF did with how other federations warned athletes of the rule change, it's a night and day difference," he added.

The chief executive - Johan Eliasch - of one of Sharapova's sponsors, racquet manufacturer Head, said "justice had been served" and called the original ITF decision "wholly unfair".

Eliasch said "there is no doubt Maria broke a rule" but he claims there are inconsistencies in the anti-doping regime and changes are needed.

"This calls into question the revelations about certain Olympic athletes who were granted therapeutic use exemptions (TUEs) for substances that could most certainly be considered performance enhancing and have been proven to be performance enhancing under significant clinical testing," added Eliasch.

"Meldonium, the substance that Maria had been taking, has yet to be proven under any significant clinical testing to have any performance enhancing benefits."

Eliasch called for "a wholesale comprehensive review and change to the anti-doping system in identifying performance enhancing drugs".

Former Wimbledon champion Virginia Wade said it was "inexcusable" for Sharapova to find herself in this situation.

However, speaking to BBC Radio 5 live, Wade added: "She's 100% right. The ITF should be more clear.

"The players need to be much more attentive and you have got to realise that, even if you are trying everything to make yourself feel better, do better, be stronger, that it has to be within the rules."

Pat Cash, the 1987 Wimbledon men's champion, said the 15-month ban was "just a little bit on the lenient side", although he believed Sharapova did not know the drug was banned.

He also accepted that Sharapova had a "fair point" when it came to the ITF.

Cash added: "There is no doubt her image has been tarnished. Her reputation will never quite be the same."

Analysis

BBC tennis correspondent Russell Fuller

"Sharapova could return to the WTA Tour in Prague or Rabat in the first week of May and, if a wildcard is forthcoming, the French Open will be on her schedule just four weeks later.

"She will be 30 by the time she returns, but 2017 will no longer be a write-off, even though it is likely to take her several months to regain her sharpness.

"The crux of the matter is that the court decided it was reasonable for Sharapova to delegate her anti-doping duties to Max Eisenbud and the IMG agency, even if on this occasion those duties were not exercised with remotely enough care.

"In the past three years, both Marin Cilic and Viktor Troicki have also successfully argued less blame should be laid at their door.

"Cas has repeatedly set a player's bar of responsibility lower than the ITF think it should be - and as a result there must be a concern some players may in future take anti-doping less seriously than they should."

(BBC)