Olympic distance runner Zane Robertson has received an eight-year ban after failing a drug test and tampering with the doping control process, the Sports Tribunal of New Zealand announced on Wednesday.

Robertson – the New Zealand record holder in the marathon, half marathon and road 10km – tested positive for erythropoietin, commonly known as EPO, at a race in Manchester, England, last May.

EPO is a hormone naturally produced in the kidneys which controls the formation of red blood cells. When administered to athletes, it can increase the amount of oxygen delivered to muscles, improving recovery and endurance.

The 33-year-old Robertson was given a four-year ban for the positive test and a further four-year ban after the sports tribunal ruled that he had “sought to subvert the doping control process.”

According to the tribunal judgment, Robertson claimed as part of his defense that he had attended a medical facility in Kenya to get a Covid-19 vaccine; instead, though, he said he was treated for Covid-19, which he claimed involved the administration of EPO.

He provided sworn affidavits from Kenyan doctors, hospital notes, a hospital report and a witness statement from a Kenyan detective to support his claims, arguing that there was “no fault or negligence” on his part.

However, Drug Free Sport New Zealand (DFSNZ), the party opposing Robertson during the tribunal, highlighted the “clinical implausibility” of the treatment the athlete said he received.

According to the judgment, DFSNZ presented evidence at the tribunal from the vice president of the medical center Robertson said he attended, who claimed that Robertson was not administered EPO at the facility, that he had not attended the facility on the alleged date, and that the medical notes submitted were not generated at the facility.

The medical center vice president also said that, of the two doctors Robertson had said treated him, one was a lab technician and the other was not employed at the facility.

DFSNZ alleged that Robertson had submitted falsified documents and false testimony – a tampering breach he chose not to contest after deciding not to rely on the evidence he originally filed, the judgment said.

“Doping denies clean athletes the chance to excel on a level playing field,” said DFSNZ chief executive Nick Paterson.

“Mr Robertson’s actions are not just deeply disappointing, but undermine the high levels of sporting integrity we see and expect from athletes who represent our country.”

In a social media post in February, Robertson said he had stopped running professionally and was enjoying the sport for “what it is” while also focusing on his business and studies.

Without explicitly mentioning the tribunal, he added: “A lot of people/companies involved in almost making me lose interest in the sport completely. A lot of things going on outside the sport also, people sometimes forget that we are humans before we are athletes!”

During his career, Robertson twice competed at the Olympics – at Tokyo in 2021 and Rio in 2016 – and won a Commonwealth Games bronze medal in Glasgow in 2014.

Following the tribunal’s verdict, Robertson is ineligible to compete in competitive sports, which includes coaching, until September 2030. His result from the Great Manchester Run in May will also be disqualified.