Nick Cummins has been released from Western Force and his national contract on "compassionate grounds" and will play rugby in Japan after the end of the Super Rugby season.

The 15-test Wallaby, a cult hero in Australian rugby, had sought a release and been granted it based on "unique family circumstances", the Australian Rugby Union (ARU) said in a statement today, without elaborating.

Cummins admitted in a statement: "My family is currently experiencing some extremely difficult times in terms of their health and wellbeing and my time in Japan will hopefully provide me with the opportunity to give back to and provide some certainty for my family during this difficult time. I now must put my own interests in the World Cup aside."

Australian media reported earlier that Cummins had signed a deal with Fukuoka-based Coca Cola West Red Sparks in Japan's Top League.

The shaggy-haired Cummins started in all three tests against France last month but his move overseas is likely to preclude him from playing in next year's World Cup in England.

"We have been working with Nick and his management team to explore ways to retain him within Australian rugby since we were notified of his circumstances," ARU chief Bill Pulver said. "Due to his unique and extreme personal circumstances, we have reluctantly made a decision to grant Nick an early release from his current contract based on compassionate grounds."

Force CEO Mark Sinderberry also declined to elaborate on Cummins' family problems. "It's hugely disappointing but I think it's ultimately more disappointing for Nick for the situation that he faces," he told reporters in Perth.

The 26-year-old Cummins was raised with seven siblings - two of whom have cystic fibrosis - by a single dad.

The departure of Cummins, a standout personality in Australian sport with his penchant for home-spun one-liners, is a blow for the local game but a huge setback for the Force, who struggle to attract and retain talent in the far-flung rugby outpost of Perth.

Sinderberry, whose recruiters have had to bring in a number of South African players to pad out the Force roster, said Australia needed to find better ways to retain talent.

“It is an ongoing problem and it has been for a number of years for Australia,” he said. "We generally find that year before the World Cup you get a lot of activity.”