Asafa Powell is planning his appeal to the Court of Arbitration for Sport after being handed an 18-month doping ban.

The sprinter was given the sanction on Thursday by a disciplinary panel of the Jamaican Anti-Doping Commission following his positive test for the stimulant oxilofrine at last summer’s Jamaican national championships.

The ruling on Powell came two days after his training partner Sherone Simpson was also given an 18-month ban after testing positive for the same stimulant at the national championships.

Both will be eligible to compete again in December because the start of the ban has been backdated to the time of the offence.

Powell gave a strongly-worded response to the news, saying: “This ruling is not only unfair, it is patently unjust.”

The 31-year-old, who held the world record for the 100 metres between 2005 and 2008, claimed that he took a legal supplement, Ephiphany D1, which was contaminated with oxilofrine.

He continued: “This is the first time in nearly 12 years of being in the sport and over 150 tests that I have had an adverse finding. It is for a stimulant, a stimulant that is only banned during competition and experts have declared has no performance-enhancing effects.

“Sanctions for a stimulant and this kind of infraction usually range from public warnings to a ban of three months, six months in the most extreme cases.

“My team has begun preparations for an appeal to the Court of Arbitration for Sport in Switzerland.

“I want to reiterate that I have never knowingly taken any banned substances.

“I did all the necessary checks before taking Ephiphany D1 and it is my hope that the CAS will prove to be a more open and fair avenue for the review of all the facts in my case.”