World Rugby’s controversial plan for a new nations championship has suffered a major blow with both the English and French clubs threatening to take legal action against the governing body, Telegraph Sport can disclose.

It is understood that Premiership Rugby and Ligue Nationale de Rugby are considering action because they regard the proposal for an annual 12-side tournament to be “in clear breach of the San Francisco agreement”, the accord struck by World Rugby in January 2017 to guarantee the structure of the global season to 2032.

Telegraph Sport has seen a copy of a letter sent by LNR chairman Paul Goze to World Rugby chairman Bill Beaumont expressing its frustration at a lack of consultation with the French Top 14 clubs over the project, also known as the “World League”, and warning that legal action could be taken unless “major concerns” were addressed.

A Premiership source said on Thursday that the English clubs were “100 per cent” behind their French counterparts ahead of crunch talks in Dublin next Thursday and had been angered that they had not been invited to take part in the negotiations, which will be attended by the heads of all tier-one unions, plus Japan and Fiji, and the International Rugby Players organisation.

Sources said English clubs were “astonished” they were not part of the process to plan the future of world rugby having been led to believe that the San Francisco accord have provided certainty for the next 12 years.