Welsh Rugby Union chairman Gareth Davies believes squeezing the Six Nations into a six-week tournament poses a health risk for players in an already congested season.
This follows England Rugby Football Union CEO Ian Ritchie's comments about possibly knocking out one of the competition's rest weeks, reducing the number of weeks from seven to six.
Davies feels that the higher intensity with which the game is played at international level these days could lengthen injury lists and ultimately dampen the competitiveness of the age-old championship.
"To squeeze it into a shorter period is potentially damaging," Davies told BBC Sport.
"Yes they are professional and very well paid but the nature of rugby being such a physical game, I think we are meddling with players' health.
"If we are looking at the intensity at which these guys play at international level these days, and the way they train in between, it's not just the playing of course.
"It's the fact you're condensing the training into a far shorter period and I just can't see any argument for shortening it."
Meanwhile, England prop Joe Marler has backed Davies' comments, saying: "If we lost a rest week – I think it's ridiculous. It's such a physical tournament."