Paris - English and French clubs announced a rival to the European Cup on Sunday, called the Rugby Champions Cup.
Clubs from the English Premiership and French Top 14 competitions had been threatening for months to create a breakaway competition if European Cup organisers European Rugby Cup (ERC) failed to find a solution to their concerns over the current competition's format.
In a statement released on Sunday, the clubs said they had asked their respective leagues to take the necessary measures to create the new competition for next season.
The new competition will be open to Celtic League teams as well.
"The announcements by Premiership Rugby and the Ligue Nationale de Rugby (LNR) on 10th September confirmed that the Top 14 and Premiership Rugby clubs had instructed their leagues to put in place a new competition in time for the 2014/15 Season," said the joint statement from English and French clubs.
"It is now confirmed that the competition will be named the Rugby Champions Cup.
"The competition will be based on the principles of qualification on merit, a strong competition format, equality between the leagues, higher commercial values for the teams and expansion into new European markets.
"The Top 14 and Premiership Rugby clubs have already confirmed their participation in the new competition and a joint working group has been created to prepare all necessary elements in good time for the 2014/15 season."
Meanwhile Premiership chief executive Mark McCafferty said he "expected" clubs from beyond England and France would sign up to the event as well.
"We've heard that other people want to be involved in European competitions, that's why we've left the door open and expect it to be more than an Anglo-French competition," McCafferty said Sunday.
He added he was confident of getting backing for the event from England's governing Rugby Football Union -- but warned a lack of RFU support would not be enough to stop the tournament going ahead.
"You can't just from a legal point of view say 'we don't want it so we're not going to approve it', especially when there's a conflict of interests," he said.
"We'll try to overcome the issues and then take it from there. We're asking for support. We'd expect that support."
The French rugby federation (FFR) took a hard line, however, dubbing Sunday's announcement "irrelevant and inappropriate" in the wake of the proposal to launch mediation.
The FFR reminded the parties that "no international match or competition involving French clubs can be organised outside the FFR's framework without prior approval".
English and French clubs have long grumbled that Celtic League teams have an unfair advantage in European competition as most of them are guaranteed entry, whereas Premiership and Top 14 teams have to fight hard just to qualify.
It means Celtic League teams can rest players ahead of big European games, safe in the knowledge that they are not compromising their participation for the next season, whereas English and French clubs face weekly domestic battles.
Only the top six in England and France are guaranteed a place in the European Cup, whereas at least 10 Celtic League sides -- including both Scottish, both Italians and a minimum of three each from Wales and Ireland -- have a free pass into the competition.
As well as seeing a fairer distribution of places between the three major European Leagues, English and French clubs also wanted a reduction in the number of teams participating in the European Cup from 24 to 20.
All these measures were rejected by Celtic League teams and the ERC, leading to an impasse that resulted in the English and French taking the drastic breakaway measure.