The former Wales rugby captain, Ryan Jones, is part of a group of players diagnosed with early-onset dementia and other irreversible neurological impairments looking to sue the sport's governing bodies.
A legal case is being issued by Rylands Law against World Rugby, the Rugby Football Union and the Welsh Rugby Union.
The group of professional and semi-professional players argue that the governing bodies were negligent in failing to take reasonable action to protect players from permanent injury caused by repetitive concussive and sub-concussive blows.
A pre-action letter of claim was issued to the same governing bodies on behalf of a group of nine players in December 2020. However, they have been unable to agree on a settlement since then, so the matter looks likely to end up in court.
A World Rugby spokesperson has said "it would be inappropriate to comment until we have received the formal details of any action being taken."
Sources have indicated the WRU felt it "impossible" to comment having not seen details of the claim.
In a joint statement World Rugby, the RFU and WRU said they took the issue of current and former players' health seriously.
They said: "We care deeply about all our players, including former players, and never stand still when it comes to welfare.
"Our strategies to prevent, identify and manage head injuries are driven by a passion to safeguard our players and founded on the latest science, evidence and independent expert guidance.
Rylands says this application for a group litigation order is the biggest 'class action' lawsuit to be launched outside the United States. It represents more than 185 rugby union players aged in their 30s, 40s and 50s.
Jones, 41, was a member of the British and Irish Lions squad on the 2005 tour of New Zealand. He revealed his diagnosis with early-onset dementia and probable CTE in an interview with the Sunday Times earlier this month.
"I feel like my world is falling apart...I am really scared because I've got three children and three step-children and I want to be a fantastic dad.
"I lived 15 years of my life like a superhero and I'm not. I don't know what the future holds.
"I am a product of an environment that is all about process and human performance. I'm not able to perform like I could, and I just want to lead a happy, healthy, normal life.
"I feel that's been taken away and there's nothing I can do.
"I can't train harder, I can't play the referee, I don't know what the rules of the game are anymore."
A statement from Rylands confirming the imminent issuing of proceedings concluded:
"This claim isn't just about financial compensation; it is also about making the game safer and ensuring current and former players get tested so that if they are suffering a brain injury they can get the clinical help they need.
"The players we represent love the game. We aim to challenge the current perceptions of the governing bodies, to reach a point where they accept the connection between repetitive blows to the head and permanent neurological injury and to take steps to protect players and support those who are injured."