The dual-code Wales international Gareth Thomas has retired from all forms of rugby with immediate effect. Thomas, whose last game of rugby was in the Super League for Crusaders on 9 July, said he took the decision after coming to the conclusion that he could no longer give 100%.

"I have listened to and discussed this decision with many of my family and close friends," he said. "My mind has told me that the time to retire is now.

"If you can't give 100% to rugby then you can't do it justice. This is a sad day but I know that my time has come to an end as a player. My passion for the amazing game will never end or leave me, however."

The news was broken by Emanuele Palladino, from Thomas's management company Distinct, only four days before the former British and Irish Lion was due to play for Wales against England in the Four Nations series.

Palladino said: "We can confirm that Gareth Thomas is officially retiring from both international and club rugby with immediate effect. This marks the end of what has been a remarkable career for a remarkable person. Gareth hopes that through his achievements both on and off the field he has left a lasting legacy within the game."

The 37-year-old Thomas switched codes from union to league with the Wrexham-based Crusaders two years ago and, following their demise, was poised for a surprise move to Wigan Warriors.

The Wales rugby league coach, Iestyn Harris, warned on Monday that Thomas was in danger of missing the Four Nations after pulling out of the warm-up against Ireland for personal reasons, but there was no indication that the player would announce his retirement.

Thomas became the first Wales rugby union player to reach 100 caps when he surpassed Gareth Llewellyn with his 100th appearance in the 2007 World Cup match against Fiji. His record was beaten by the fly-half Stephen Jones, however, who won his 104th cap at the 2011 World Cup but Thomas remains the second most-capped Wales international.