Top English and French clubs have hinted at possible legal action against World Rugby's proposals for a world league.
Their move comes as representatives from the major unions and player associations meet in Dublin to discuss plans to take the international game forward with a meaningful test championship.
The suggested world league involves 12 teams based largely around combining the Six Nations and Rugby Championship on an annual basis.
Japan and Fiji look set to join the southern group with World Rugby insisting rankings will be used to determine the makeup and that promotion relegation will be involved.
But in a joint statement Premiership Rugby of England and their French counterparts, says their clubs feel World Rugby's proposal runs against what was agreed for a long‑term vision at a meeting of major stakeholders in San Francisco in 2017.
Stuff.co.nz reports the two club organisations are unhappy at not being involved in the Dublin meeting given the impact any new test championship is likely to have on their competitions and players.
The French and English clubs are unhappy at what they believe will be a heavier test programme in November and December that will impact their tournaments.
World Rugby believes otherwise, claiming the new format will mean an increase in matches only for the teams that qualify for the finals.