Miles, 57, started his career in race calling at the ABC in 1979. The Victorian metropolitan race caller completed his 36th Melbourne Cup call this year.

His announcement has come as a shock to many in the industry, who believe he has much more to give racing, going forward.

"I know I might be leaving a little early, but I'd rather leave two years early than two years late," he said.

"My contract ends in June, I'll still be doing radio and TV work, and I'll be on the panel to select my successor."

Miles said he would be ending his career on his own terms. He will continue with his current calling schedule until his retirement after which time he will work on a series of projects for Racing.com as part of its daily free-to-air broadcast of Victorian racing.

"I have been privileged to call Australia's greatest races for more than three decades and after a long and fruitful career I believe that the time is now right to announce my pending retirement from race calling and allow a period of transition for the industry to its next metropolitan race caller," he said.

"I have always wanted to conclude my calling career on my terms and I will depart the caller's box next June satisfied with my performance throughout this year's spring racing carnival.

"I have enjoyed longevity in my role due to the wonderful support afforded by my family and so many great people in racing and I want to collectively acknowledge those people whom I will thank personally."

No comedy and only a very occasional smile and a joke ever creep in when Miles spends a day calling races, perched high above the crowd. He is the voice of Victorian racing; he is the bearer of good news and bad news, whatever way a tricky photo finish might go.

As Victoria's premier caller, Miles calls all metropolitan race meetings (Wednesday, Friday night and Saturday) along with major country cups.

He came up in the days of vintage race callers such as Bill Collins OAM, Bert Bryant and Miles' long time mentor, Joe Brown.

Miles called his first Melbourne Cup in 1981 at the age of 22 and bettered the record of the late Collins when he called his 35th consecutive Melbourne Cup in 2015.

His responsibility to his audience has never been lost on Miles. He will fuss over a minor placing photo finish because a certain core of his listeners will be hanging on the result. Miles, a noted perfectionist, takes the smallest blemish in his calls to heart.

Racing Victoria CEO Bernard Saundry congratulated Miles on his career

"As a racing fan at heart I have been blessed to grow up listening to Greg call our greatest races. He has transcended generations and will leave hefty shoes to fill when he officially retires," Saundry said.

"Greg can be most proud of his professionalism and commitment throughout his career and know that his ability to capture the moment has played an integral role in creating some of our greatest racing memories.

"To honour Greg's career, it is our intention over coming months to develop a scholarship for aspiring racecallers that will be named in his honour and which he will play an active role in nurturing emerging talent."

It is understood that tens of millions of people heard Miles' call of this year's Melbourne Cup, with the broadcast going around the world.