Paris - European Club Rugby (ERC) president Jean-Pierre Lux has accused English and French clubs of using "guerilla" tactics in the ongoing row over the format of the European Cup.
Lux said the English and French teams were not showing any willingness to compromise in their demands, but he rejected the idea that they could form a breakaway competition next season.
Clubs from the English Premiership and French Top 14 have said they will pull out of the European Cup next season and set up their own competition, in which they will invite other teams to take part, if they don't get their way over the current impasse.
They want a reduction in the total number of clubs taking part in the European Cup from 24 to 20, as well as a significant cull in the number of Celtic League teams gaining automatic entry, from 10 to six.
But Lux says they're being unfair in their demands.
"There were meetings up to the beginning of June. Since then everyone has been waiting for someone else to make the first move to kick-start the negotiations," Lux said.
"We received letters from the English and French leagues a few weeks ago that had a decidedly guerilla spirit to them.
"When I hear the English and French leagues denouncing Celtic intransigence, we could also reply that those two leagues don't want to change their positions.
"We need to find a compromise to advance."
Even so, Lux says there's no chance a rival competition could be organised next year, despite Anglo-French threats.
"It's not possible. I went to a meeting last week where the chief executive of the English (Rugby) Federation Ian Ritchie and the president Bill Beaumont clearly said they had told their clubs there would be no new society.
"Pierre Camou (president of the French Rugby Federation) has clearly indicated in France for some time that there will never be a Franco-English competition, he's against it.
"All the federations hope that ERC continues to run the (European) competitions."
Lux says that the Anglo-French proposals would have a detrimental effect on the game in Europe.
"Going from 24 to 20 clubs in the European Cup means the Scottish and Italian teams would lose out," he said.
"I've been told it would improve the level of the Challenge Cup (as that would move from 20 to 24 teams) but I remain sceptical because we're asking for those four teams to come solely from the Celtic League.
"I would prefer all the leagues to make an effort."
Current rules mean that 10 out of the 12 Celtic League teams are guaranteed entry into the European Cup, including both Scottish and both Italian teams, while depending on who wins the two European competitions, all 12 could qualify.
The English and French leagues are only guaranteed six each.
This season saw 11 out of the 12 Celtic teams qualify, with only Newport Gwent Dragons from Wales missing out.
This season's Challenge Cup contains seven French teams, six English, four from the Italian top flight, one Portuguese, one Romanian and just one from the Celtic League, the Dragons.
The English and French teams tend to play their reserve sides against the other European teams and still canter to high-scoring victories.
What they want is to see six teams from each of the English, French and Celtic leagues qualifying for the European Cup by their league position, with the final two teams coming from the countries whose sides win the European Cup and Challenge Cup.
They feel that the current format favours Celtic League teams who know they can rest their best players in league matches ahead of European Cup games as they are not risking their participation in the competition the next season, whereas in England and France every game is a battle to ensure a high enough league finish.