Former head of the World-Anti-Doping Agency Dick Pound says Maria Sharapova's claim she missed emails about rule changes won't work in her defence after failing a drugs test.

The former world number one says the substance found in her sample is from medicine she has been taking for years.

It was only put on the banned list in January.

Pound says the fact it has been used for health reasons might mean a less severe punishment, but is less sympathetic when it comes to the claim of Sharapova not knowing about the rule change as he told BBC Sport.

"Leaving aside the fact you're running an $30million annual business, which becomes eligible on you being able to play tennis, and you're taking something that's on a list that you've known about for four months? I'm sorry - that is a big mistake," he said.

Dick Pound, former @wada_ama president:#Sharapova seemed to ignore meldonium ban for unknown reasons #SkyNewsTonight https://t.co/WW8iIe0z9j

— Sky News Tonight (@SkyNewsTonight) March 8, 2016