Improving trust in anti-doping rules is a priority for the International Tennis Integrity Agency after several high-profile cases last year raised doubts over its processes, CEO Karen Moorhouse said in the ITIA's annual review.
Men's world No 1 Jannik Sinner accepted an immediate three-month ban in February after reaching an agreement with the World Anti-Doping Agency (Wada) which appealed against the decision of an independent tribunal to clear him of any wrongdoing after a positive doping test.
Poland's five-time Grand Slam champion Iga Swiatek accepted a one-month suspension in November having tested positive for banned substance trimetazidine (TMZ) which she said was the result of contamination of her sleep medication.
The speed with which Sinner and Swiatek's cases were dealt with, and the leniency shown, cast a spotlight on the anti-doping system after former world No 1 Simona Halep criticised officials for lengthy delays in her own case.
"(The Jannik Sinner) case has invariably raised further questions about the anti-doping process in tennis," Moorhouse said in the report published on Thursday. "We – alongside our funders – are determined to answer them, and drive deeper understanding of the work we do within the sport.
"The complexity of the system is one of the many reasons why it's important that we continue to work together with our members and tennis stakeholders to build trust."
Accusations of double standards were aimed at the ITIA while 24-times Grand Slam champion Novak Djokovic said there had been a lack of consistency and transparency in the cases while Australian Nick Kyrgios described the Swiatek and Sinner cases as "disgusting" for the sport.
The Professional Tennis Players' Association (PTPA), which this month filed a lawsuit against tennis's governing bodies, accuses the ITIA of violating players' privacy rights with random drug tests.
The ITIA's review highlights a 26 per cent increase in anti-doping tests in 2024 compared to the previous year with 9 151 being carried out. It says educating players about anti-doping rules, especially the risk of contaminated supplements, was a major pillar of its strategy for the next three years.
"The past 12 months has reinforced the challenges involved for players and their support teams," ITIA Anti-Doping Senior Director Nicole Sapstead said. "30 per cent of anti-doping rule violations in tennis over the past 15 years can be attributed to contaminated supplements, and there is work to be done.
"It remains our view that the vast majority of players compete clean, and the largest proportion of TADP (Tennis Anti-Doping Programme) cases involve unintentional doping."
Sinner, who won his third Grand Slam title at this year's Australian Open despite uncertainty about Wada's appeal, tested positive for anabolic agent clostebol at last year's Indian Wells and Miami tournaments, with the Italian saying it had entered his system from a member of his support team through massages and sports therapy.
His ban will end on 4 May.