Simona Halep questioned the "big difference" in how doping cases are treated after world No. 2 Iga Swiatek was handed a one-month ban while the Romanian was out of action for over 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 tested positive in August, but the ITIA, which runs tennis' anti-doping program, accepted that it was caused by contamination of her medication melatonin.