The rider, who enjoyed Grade One glory with Sam Spinner in the 2017 Long Walk Hurdle, admitted he had taken the drug the weekend before riding on February 23.
He was jailed in 2016 for lying about the circumstances of a drunken car crash and was the banned from driving for 40 months after pleading guilty to drink driving in 2019.
Colliver’s urine sample was found to contain benzoylecgonine, a metabolite of cocaine, in a quantity of 1,650ng/ml which is in excess of the permitted level of 150ng/ml. His interim suspension began on March 4, meaning the six-month suspension ends on September 3.
Charlotte Davison, representing the British Horseracing Authority at an independent disciplinary panel hearing on Thursday morning, acknowledged Colliver’s immediate admission that he had taken the drug when interviewed in May.
Sheffield-born Colliver, who predominantly rides for Middleham trainers Micky Hammond and Jedd O’Keeffe, was represented by solicitor Rory Mac Neice, who underlined the rider’s remorse.
He said: “Mr Colliver has asked me to convey in clear terms how very sorry he is that this has happened.
“He is very keen to publicly apologise to owners and trainers who have supported him throughout his career, but also to the stable staff. He has instructed me that their support has always meant a huge amount to him and continues to do so.”
In imposing the ban, panel chairman James O’Mahoney said: “Racing for jockeys is a hard and tough profession, we are aware of that, but there is a real purpose in the severity of the penalty for people taking cocaine in racing and putting others and horses at risk.”