Former Olympic champion Audley Harrison has announced his intention to retire from boxing.

The 43-year-old, who won gold at the Olympic Games in Sydney 15 years ago, initially retired from the sport in May 2013, but reversed his decision three weeks later.

Harrison had planned a comeback fight this year, but after researching the long-term effects of concussion and head injuries, the boxer has opted to hang up his gloves.

Via his official website, Harrison said: "My boxing career has come to an end. I am no longer a professional boxer and that is good with me. After locking myself away for the last five weeks, I've tried to focus and turn back the clock to get myself into fighting condition.

"I've also seen specialists for my brain, eyes and various other experts to test my body functions in regards to strength, power, speed, reaction time, cognitive function and agility. Additionally, I looked at the latest research into concussions and traumatic brain injuries (TBI). After years of denial and sticking to my guns, I'm finally getting out of my own way. As tough as it is to say this - it's time to stop.

"So, no world title for me as a boxer, but I accept that outcome as my lesson I had to learn. I was certainly talented enough to do it, but that ingredient is never enough. My desire to control my career and beat the system broke me down - I was desperate to do it, but not for any promotor but own my company A-Force Promotions. So be careful what you put out into the universe as the law of attraction is real.

"I'm blessed and grateful for this journey and want to thank all those individuals who have participated in my growth and success along the way. Although I was difficult, I truly appreciated your support, assistance and counsel. It's been fun my friends - tough and as real as they come, but I wouldn't have it any other way."

Harrison's last fight ended in defeat to Deontay Wilder in April 2013.