Former middleweight champion Barker retires
Britain's Darren Barker poses during the official weigh-in his IBF world middleweight bout against Felix Sturm in Stuttgart, Germany, on December 6, 2013
The 31-year-old took the IBF title with a points win over Australian Daniel Geale last year, only to lose his first title defence against Felix Sturm in December after a long-standing hip problem flared up.
"I'm so proud and happy at what I've achieved," said Barker, who dedicated his success to his late brother, Gary.
"When I won my first national title as a kid I could have retired a happy boy then, so to have won all the major titles possible for me, I'm a very, very happy man.
"I did this all for my brother Gary -- we did it mate! I'm now looking forward to sitting back and being a keen fan and wishing all my fellow countrymen all the best in their careers."