Sonny Bill Williams stripped of WBA and NZ heavyweight boxing titles

Former All Black Sonny Bill Williams has been stripped of his professional boxing belts after the dual code rugby international failed to defend his world and New Zealand heavyweight titles.

Williams, 28, is eyeing a return to rugby union in 2015 hoping to be part of New Zealand's World Cup defence and the national sevens team at the 2016 Olympics in Rio de Janeiro.

His new goals have forced the suspension of his boxing career during which he won all of his six professional heavyweight bouts.

This has prompted the World Boxing Association to declare vacant the heavyweight title, which Williams won in controversial circumstances over South African veteran Francois Botha in February.

The New Zealand Professional Boxing Association (NZPBA) has also stripped Williams of his heavyweight belt after he failed to respond to challenges. "We haven't heard a thing back and, personally, that's rude," NZPBA president Lance Revill, said. "He has not even said he's received the challenge and that they're going to think about it. If that was the case we'd hold off, but we've got no choice now but to strip the title."

NZPBA secretary Pat Leonard said the body tried several times to contact Williams' Australia-based manager Khoder Nasser without success.