There is more doping in athletics now because the potential prize money available is "bigger than ever", according to a former US sprinter who was himself banned from the sport in 2005.
Tim Montgomery was speaking after a decision today to ban the Jamaican sprinter Asafa Powell for 18 months after he tested positive for the stimulant oxilofrine.
Montgomery said he could not see why an athlete would "go into a competition not knowing what they're taking".
Jamaican sprinter Asafa Powell has issued a statement calling his 18-month ban for taking a banned substance 'patently unjust'.
Powell, 31, said he had unknowingly taken oxilofrine when he was using a legal supplement called Epiphany D1.
He added that his team had contacted doping authorities to point out that oxilofrine was not listed as an ingredient for Epiphany D1.
The former world record holder also questioned the severity of his punishment, claiming it was "clearly not based on the offense nor the facts surrounding it".
Powell's team is now preparing to take his case to the Court of Arbitration for Sport in Switzerland.
Former 100 metres world record holder Asafa Powell has been banned from athletics for 18 months for doping.
The 31-year-old Jamaican sprinter has competed at the last three Olympics and broke the world record in 2007 when he ran the 100 metres in 9.74 seconds at an event in Italy.
Powell tested positive for a banned substance in July of last year.