• Ian Ritchie says failure will affect all six nations • Welsh regions to tell WRU they will go own way

Ian Ritchie, the chief executive of the Rugby Football Union, has warned that failure to reach an agreement on a European club tournament next season would have serious consequences for the game in all of the six nations, accusing the French of sabotaging an accord last month that would have saved the Heineken Cup.

With the English clubs refusing to play in the Heineken Cup next season and the Welsh regions ready to defy their union on Wednesday by refusing to sign a new participation agreement, Ritchie fears that 18 years of European club rugby could come to an abrupt end to the benefit of no one.

"We must make one more effort to get an agreement for next season," Ritchie said. "We should all bust a gut to get there because failure would not be a good number. We had reached an understanding last month that the Six Nations committee would operate the tournament, with clear roles for unions and clubs, but the only one not to sign up for it was the French Rugby Federation [FFR]."

The plan, which followed weeks of conversations and meetings between Ritchie and the other Heineken Cup stakeholders, hinged on the Six Nations committee taking over as the tournament organisers from European Rugby Cup Ltd, a body Premiership Rugby says it will have nothing to do with after this season, not least because the two organisations have television deals with the rivals BT and Sky.

Ritchie said that the agreement gave the four RaboDirect Pro 12 unions a guaranteed income for five years of more than €100m (£83.8m) with any drop in the projected income in that period borne by the French and English clubs who, in return, would run the commercial arm of the tournament.

"Unfortunately, the French have always been reticent about the Six Nations committee because of their association with Fira [the organisation representing the smaller European unions] and they wanted a new company to be formed to run the tournament," Ritchie said.

The Top 14 and Premiership clubs gave notice 18 months ago that they would be pulling out of ERC at the end of the season, along with the FFR, but it was the French who last month suggested, at a meeting of all the ERC unions except the English in Dublin, that the Heineken Cup carry on under the same organisation for another season, giving time for talks over the federation's plan for the Six Nations committee to be replaced by a Uefa-style governing body based in Geneva.

"I do not know why we were not invited and I was pretty unhappy after all the attempts we had made to fund a solution but it has not stopped us from trying to get all the stakeholders around the table again," Ritchie said. "I do not think a transition year is the answer and after reaching agreement over issues such as meritocracy and financial distribution, we must all make one final push."

The prospects of an agreement are not healthy. Time is running out with no meeting scheduled and while the Premiership clubs are prepared for the Six Nations committee to take over from ERC, the French sides agree with their union that new organisers of the Heineken Cup should be part of a shake-up of the way the whole game in Europe is run.

"It all comes down to the framework, who runs it," Ritchie said. "ERC, the Six Nations or a new company. We believe the Six Nations is perfectly acceptable and so do Premiership Rugby and the Ligue Nationale de Rugby, but the FFR does not. We have to find a solution.

"We must all understand the consequences of failure because none of the alternatives to a pan-European tournament is good. I urge everybody to get talking again because it is still possible to get this thing agreed for next season."

Ritchie denied that the RFU was merely doing the bidding of its clubs, saying that he did not agree with all of their tactics in the dispute but that a close relationship with them was vital for the English, and added that he thought it more unlikely than not that an Anglo-Welsh league would next season fill the vacuum left by Europe.

The Welsh regions are expected to tell the Welsh Rugby Union on Wednesday that they will be going their own way next season, prepared to go to court to fight for the right to link with the English. "It is the most important day in Wales in the professional era," said Simon Easterby, the Scarlets' head coach.