Former England coach Clive Woodward has criticised Wales and Australia for only naming two hookers in their 31-man World Cup squads.
Australia have included Stephen Moore and Tatafu Polota-Nau, while Wales have named Ken Owens and Scott Baldwin as their two No.2s.
If any of these players become injured, a replacement is allowed to be called up but not included in a squad within 48 hours of their arrival. This means that uncontested scrums could potentially occur during games.
"What is going on here is open to interpretation, but it is just so wrong," Woodward wrote in his Daily Mail column. "Since the last World Cup the size of the squads has been increased from 30 to 31 specifically to allow for an extra front-row forward to be included for well-founded safety issues.
"There are real safety concerns. If we want proper scrummaging contests - and everybody seems agreed that we do - we must also have proper player welfare measures. That is non-negotiable. Every squad must have three specialist hookers and it should be mandatory. And I am sure that is what RWC intended even if they seem to have left a loophole by actually insisting on just six specialist front-row forwards in a matchday 23.
"I look at Wales and Australia naming just two hookers and I wonder if they are being really fair to their own players, let alone the opposition, and the paying public."
World Rugby states that a matchday squad of 23 players must consist of six front-row players - three starters and three replacements - who are suitably trained and experienced in that position.
