McDevitt joined the organisation in 2014 as the replacement for Aurora Andruska, having previously served in law enforcement for 28 years with ACT Policing, the Australian Federal Police, Royal Solomon Islands Police and the Australian Crime Commission.

He has opted against serving for a further three-year term at ASADA, with the official informing Australia’s Minister for Sport, Greg Hunt, of his decision.

"My time with ASADA has been both challenging and rewarding," said McDevitt, whose term will end on May 9.

"I have had the opportunity to work with people who are very passionate and committed to clean sport, and I have no doubt they will continue this work in the face of new challenges domestically and globally.

"My experience has convinced me that we face an ongoing threat of doping.

"It is more sophisticated, more readily available and harder to detect.

"There are people willing to push the boundaries with experimental substances and methods which have not been clinically tested or approved for human use.

"The 'win at all costs' mentality harms athletes, destroys fair play and equitable competition and does irreparable damage to the credibility of sport.

"ASADA is trying its best to protect clean athletes and their right to compete on a level playing field."

During McDevitt’s tenure at ASADA, the organisation faced several notable challenges, including the scandal surrounding Australian Football League (AFL) club Essendon, whose record of 16 Premiership titles is the best in the sport's history.

Thirty-four players from the club were banned after doping charges.

The case was born out of an investigation in February 2013 by the Australian Crime Commission, which released the Organised Crime and Drugs in Sport report alleging widespread doping in Australia.

In June 2014 ASADA initiated action against the players, via the AFL Anti-Doping Tribunal, alleging doping through the use of the banned peptide Thymosin Beta-4.

An AFL Anti-Doping Tribunal initially ruled there was insufficient evidence to find the players guilty of offences arising from the club’s controversial 2012 supplements programme, but the the World Anti-Doping Agency successfully appealed the verdict at the Court of Arbitration for Sport.

Sports scientist Stephen Dank was also handed a life-time ban for multiple doping offences, despite being cleared of injecting any Essendon player with Thymosin Beta-4.

His 10 doping convictions were linked to trafficking and possessing banned substances during his employment with Essendon and earlier work with the Gold Coast Suns at the back end of 2010.

McDevitt, who labelled the Essendon case as the "the most devastating self-inflicted injury by a sporting club in Australian history", warned that Australia needed to guard the country’s reputation for fair play.

"Sport is a multi-billion dollar industry in Australia," McDevitt said.

"We have to protect the integrity of that industry. 

"Beyond dollars though, the reputation of Australian sporting excellence and the achievements of our athletes is just extraordinary and we have to jealously guard our reputation for fair play.

"I am sure that ASADA will continue to work hard with sporting codes and the 85 sports who have anti-doping policies to help them to target harden their sports and thereby their reputations.

"There is a growing realisation that an investment in sports integrity should be viewed not as a business cost but as a business enabler.

"During my tenure, I am proud to have overseen a number of positive changes for ASADA and more broadly sport in Australia, including the redevelopment of ASADA’s Operating Model and the enhancement of our intelligence and investigative capabilities, enabling us to better target those high-risk sports and individuals."

ASADA, which claimed they had conducted the "most rigorous" anti-doping programme of any Australian Olympic team to date before Rio 2016, admitted that their budget was slashed by 20 per cent last May before the Games.