Rugby players from the South Pacific islands are being caught up in a tug-of-war because their European clubs place "undue pressure" on them not to play international matches, the chief executive of the global players' union said.
Omar Hassanein, of International Rugby Players, said that the national team of Samoa had even been deprived of players at last year's Rugby World Cup - a situation which would be unthinkable in the football equivalent.
World Rugby's Regulation 9 dictates that players must be released by clubs for internationals, but it is not always cut and dried for professionals from outside the top tier of nations.
Clubs sometimes try to get around the rule by implicitly promising a bonus or contract if players skip international matches, while the out-of-contract players are even more vulnerable to pressure.
"The Pacific nations of Tonga, Fiji and Samoa struggle to get hold of their players and that is going to continue because the player needs to put food on the table," Hassanein told Reuters on the sidelines of an International Labour Organisation conference on athletes' rights.
"Regulation 9 is a constant dilemma for us, because it's not only about how it is drafted but also how it plays out, when clubs put undue pressure on players not to play international rugby."
"We can't hide from the fact we had a Rugby World Cup, a showcase event last year, and players from Samoa, particularly, were being in held in the club system during our flagship event. That is not where we want to be."
Samoa winger Belgium Tuatagaloa told Reuters before the World Cup that he faced the choice of playing at the tournament or signing a new club contract: he chose the World Cup.
Samoan lock Joe Tekori announced his international retirement two months before the tournament in Japan to focus on his club career with Toulouse while English-based Michael Fatialofa, Melani Nanai and Jordan Taufua opted out.
At the same time, Pacific Rugby Players (PRP) union chief executive Aayden Clarke said he knew of players whose clubs, having released them for the World Cup, were ringing them daily to entice them to turn their backs on their countries.
Hassanein, who said that the three South Pacific nations provided 18 percent of all professional rugby players between them, said that clubs should be more involved in discussions around a global calendar.
"The international game and the club game are not interdependent and there is no greater example than the Pacific Island nations," he said.
"The club and international scene have to be properly aligned and we are not near where we need to be in that respect -- and the players are the ones caught in the middle."