Simona Halep questioned the “big difference” in how doping cases are treated after the world No 2, Iga Swiatek, was handed a one-month drugs ban while the Romanian was out of action for more than 18 months following two separate anti-doping violations.

The International Tennis Integrity Agency (ITIA) said on Thursday that Swiatek had accepted a one-month suspension after testing positive for the banned substance trimetazidine (TMZ). The Pole, 23, tested positive in August but the ITIA, which runs tennis’s anti-doping programme, accepted that it was caused by contamination of her medication, melatonin.

Halep, 33, was provisionally suspended in October 2022 and later banned for four years, a period which was reduced to nine months last March after an appeal at the court of arbitration for sport. She had strongly denied knowingly taking the banned substance roxadustat and said she had evidence to show small amounts of the anaemia drug entered her system from a contaminated licensed supplement.

“I stand and ask myself, why is there such a big difference in treatment and judgment?” Halep, the former world No 1, said in a post on Instagram. “I can’t find and I don’t think there can be a logical answer. It can only be bad will from the ITIA, the organisation that has done absolutely everything to destroy me despite the evidence … It was painful, it is painful and maybe the injustice that was done to me will always be painful.”

The ITIA said all cases were dealt with based on facts and evidence, not a player’s name, ranking or nationality. No two cases are the same, they often involve different circumstances, and direct comparisons are not always helpful. There are some very important differences in these two cases,” the ITIA said.

“The product contaminated in Swiatek’s case was a regulated medication, not a supplement. There was agreement among independent scientific experts surrounding the facts and the player admitted the anti-doping rule violation.

“We urge players to exercise extreme caution when taking supplements and we are always happy to answer any questions they have.”

Halep, the former Wimbledon and French Open champion, had criticised the tennis authorities for the length of time it took to process her case. After her provisional suspension in October 2022, she received her four-year ban in September 2023.

Swiatek, who was world No 1 when she failed the test, was provisionally suspended on 12 September, but had it lifted on 4 October, leaving her with just over a week’s ban to serve.

Players on both tours called out what they perceived as double standards in the sport when the men’s world No 1, Jannik Sinner, was cleared of wrongdoing despite failing two drug tests earlier this year. An independent tribunal accepted the Italian’s explanation that the anabolic agent clostebol had entered his system from a member of his support team through massages and sports therapy. Sinner could still be banned for up to two years with the World Anti-Doping Agency appealing against the decision in his case at sport’s highest court.

Amid questions about the handling of the cases of Swiatek and Sinner, ITIA chief executive, Karen Moorhouse, said: “These aren’t cases of intentional doping. We’re dealing with inadvertent breaches of the rules. So I don’t think this is a cause for concern for tennis fans. The fact that we’re being clearly open, transparent, and it shows the breadth and depth of our anti-doping programme.”

The Professional Tennis Players Association (PTPA), which was established by Novak Djokovic and Vasek Pospisil in 2020, said late on Thursday that tennis needed an anti-doping system rooted in transparency, consistency and objectivity.

“Players deserve and are entitled to due process and support in navigating the anti-doping system, regardless of ranking and access to resources … (They) deserve and are entitled to governance that they trust,” the advocacy group added. Our fight to overhaul the failing tennis system continues.”