The then 23-year-old was sent home from the Brazilian Games after testing positive for banned substance methandienone.

He admitted taking a supplement but said that he had ingested the substance inadvertently. 

However, the Irish Sport Anti-Doping Disciplinary Panel ruled that he had been unable to prove that the doping violation was not intentional. 

According to RTE, the laboratory "reported that while the product contained methandienone, the concentrations were not consistent with the timeline of events asserted by Mr O'Reilly".

His ban has been back-dated to July 11, 2016, the day of his failed test when he was provisionally suspended.

It means the now 24-year-old will not be eligible to box again until July 10, 2020.

O'Reilly underwent a random test conducted by Sport Ireland prior to flying out to Brazil for the Olympics with the rest of the country's boxing team.

In a statement given to RTE at the time, he said that he unintentionally took a supplement that may have contained a banned substance.

It added he was given it "by someone unrelated to his team or association".

The statement also said O'Reilly apologised to his fellow boxers, team-mates, the Irish Athletic Boxing Association, Sport Ireland, the Olympic Council of Ireland and "all those who have supported" him.

After being informed of the test results, O’Reilly was forced to stay outside the Olympic Village and have no contact with his team-mates while he considered whether to appeal and request a B-sample.

O’Reilly was considered one of Ireland's best hopes for a boxing medal after winning middleweight gold at the 2016 European Games in Azerbaijan's capital Baku.

He also won World Championship bronze in 2015.