The 31-year-old, the 2011 world champion and 2010 Commonwealth Games gold medallist, tested positive for the stimulant methylhexaneamine after finishing fourth. 

Montsho was informed at the decision of the end of last month but it has only been made public after it was studied by the International Association of Athletics Federations.

She received only a two-year ban, rather than four, because her offence was committed last year before the new World Anti-Doping Code came into effect on January 1, 2015.

Montsho had denied taking everything that was banned deliberately, blaming a contaminated supplement for the postive test, but a disciplinary panel set-up by the Botswana Athletics Association and which included a lawyer, medical doctor and sports physiologist still recommended the two-year ban. 

Amantle Montsho became a national heroine in Botswana when she won the gold medal in the 400 metres at the 2011 World Championships in Daegu ©Getty Images

The ban is a huge stain on the career of Montsho, whose victory in Daegu in 2011 made her the first athlete from Botswana ever to win a world or Olympic title.

After finishing fourth in the Olympics at London 2012, she narrowly failed to retain her world title at Moscow a year later when she led for most of the race only to be pipped on the line by Britain's Christine Ohuruogu. 

Montsho also won consecutive gold medals in 2007 and 2011 at the All-Africa Games and claimed victory at the African Championships in 2008, 2010 and 2012. 

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