A review set up by the agency has censured it for failing to pursue claims that a doctor supplied drugs to more than 150 athletes
UK Anti-Doping (UKAD) has been heavily criticised for its handling of information relating to a doctor who was allegedly supplying athletes with banned substances.
The agency, a national organisation committed to drug-free sport, commissioned an independent review after claims aired in the Sunday Times that Dr Mark Bonar had provided more than 150 elite athletes with performance-enhancing drugs.
Amateur cyclist Dan Stevens turned whistleblower in the hope of reducing his suspension after he was banned for two years for breaching anti-doping rules in 2014.
But the review's report censured UKAD for failing to pursue claims against Bonar and for not contacting his professional body, the General Medical Council.
While praising UKAD staff for their "transparency" and commitment to clean sport, the report was scathing about certain parts of the investigation into Bonar.
"It is difficult to understand why no contact was made with the GMC when that course of action was suggested on at least seven occasions either by members of UKAD, the athlete (Stevens) and his legal representatives," said the review's chairman, former Merseyside assistant chief constable Andy Ward.
He added that "as a minimum standard of investigation, a simple check" with the GMC should have been made to find out if it, as Bonar`s regulatory body, had any information that could "support or negate" Stevens claims.
UKAD was also criticised for not giving Stevens a more lenient sentence after his cooperation, with Ward highlighting the "confusion and lack of clarity" as to how the agency deals with dopers seeking to reduce their sanction in return for "substantial assistance".
He described UKAD's dismissal of Stevens request for a lesser punishment as "harsh" and "subjective".
That dismissal prompted Stevens to take his story to the Sunday Times, which then filmed the London-based Bonar claiming he had supplied prohibited drugs to more than 150 top-level athletes.
Those claims, which were published by the newspaper in April, have now been investigated by UKAD, and the agency did eventually share its findings with the GMC. Bonar has since denied any wrongdoing.
"It is clear that opportunities to gather intelligence, secure evidence and investigate Bonar have been missed," Ward concluded.