Olympic gold medallist Anthony Joshua is expected to turn professional this week after leaving the Great Britain amateur boxing programme with immediate effect on Wednesday.
Joshua shot to prominence when he defeated Roberto Cammarelle in the super-heavyweight final at the London Games last year.
The 23-year-old is set to sign for Eddie Hearn's Matchroom organisation.
It means Joshua could make his debut on the undercard of Carl Froch's world super-middleweight title clash with George Groves later this year, which is being promoted by Hearn.
The British Amateur Boxing Association said in a statement: "BABA has confirmed that the 2012 Olympic super-heavyweight gold medallist, Anthony Joshua MBE, will not be part of the GB Boxing squad in the 2013-17 Rio cycle.
"His contract with the BABA finished at the end of the 2009-2013 London Olympic cycle and he has now left the World Class Performance Programme to pursue other career opportunities."
Great Britain performance director Rob McCracken added: "Anthony is a very talented sportsman who has enjoyed a meteoric rise to become Olympic champion, less than four years after he first began boxing.
"Naturally, it is a disappointment for us that Anthony has decided his future lies away from the GB Boxing programme, but he departs with our very best regards and we wish him every success in his future career."
Joshua had been training at the Great Britain squad's gym at the English Institute of Sport in Sheffield while he considered his options in the wake of his Olympic triumph.
He is be the fourth member of Great Britain's 2012 Olympic boxing team to turn professional, following gold medallist Luke Campbell, middleweight bronze medallist Anthony Ogogo, and Thomas Stalker.