LONDON, March 21, 2018 (Reuters) - Britain's WBO middleweight champion Billy Joe Saunders has postponed his title defence against Martin Murray next month after suffering a hand injury in training. The fight with compatriot Murray was scheduled for London's O2 Arena on April 14 but will now take place on June 23. Saunders has defended his title three times, most recently against David Lemieux in Canada in December. "I felt my hand go during a session this week and sought medical advice immediately," he said. "Unfortunately, I've been told that I can't punch anything for four weeks so we've been left with no choice but to withdraw from the date. My trainer Dominic Ingle will make sure I'm fit and prepared to put on another show on June 23rd." In another development, world middleweight boxing king Gennady Golovkin accused rival Saul "Canelo" Alvarez of doping, rubbishing the Mexican fighter's claims that he had failed a recent drugs test due to contaminated meat. In explosive comments to reporters at his secluded mountain training camp in Big Bear, east of Los Angeles, Golovkin said Alvarez had benefited from preferential treatment throughout his career by authorities in Nevada, where the two men will fight in a much anticipated rematch on May 5. The hard-hitting Kazakh was widely believed to have won last September's first battle against Alvarez, when a judging controversy dominated the aftermath of the bout. While one judge scored the fight for Golovkin and another had it even, there was astonishment at the card of a judge who marked it 118-110 in favour of Alvarez. Alvarez earlier this month was revealed to have tested positive for clenbuterol, which his promoters blamed on consumption of drug-tainted meat in his native Mexico. The Golovkin and Alvarez camps are awaiting a formal ruling on the case from the Nevada State Athletic Commission, but the fight is expected to go ahead. Golovkin on Tuesday emphasised that he was willing to climb into the ring with Alvarez regardless of the outcome of the Nevada case. But he pulled no punches in branding Alvarez a dope-cheat, laughing off the Mexican's claims that clenbuterol had entered his system inadvertently. "Forget Mexican meat," Golovkin said. "Come on. I told you. This is not Mexican meat. Ask him. Ask his team, his promotion. Everything.