Maria Sharapova has failed a drugs test at the Australian Open.

The former world No.1 told a news conference on Monday she had recently received a letter informing her she had failed a drugs test at the Australian Open.

The 28-year-old Russian, a five-times grand slam champion, has not competed since she lost to Serena Williams in the quarter-finals of the Australian Open in January and has struggled with a series of injuries in recent years.