Europe's most prestigious competition, the Heineken Cup, is facing a boycott by England's clubs.
The governing body of England's top clubs, Premiership Rugby, revealed on Monday that they have "given notice" of their intention to pull out of the Heineken Cup and Amlin Challenge Cup.
"Following recent media interest, Premiership Rugby confirms that it has given notice, effective 1st June 2012, under the terms of the European Rugby Cup (ERC) Accord and understands that notice has also been served by other parties to the Accord," the statement said.
The move comes on the back of long-standing disagreements over how Europe's major competitions are organised.
Premiership Rugby said their notice period expires at the end of the 2013/2014 tournament - at which time, therefore, "the Accord will terminate".
That means they will pull out of all competitions.
"We hope that there will now be an urgent dialogue about the future of European cup rugby, including qualification, competition formats and ambition to expand into new markets," said Premiership Rugby Chief Executive Mark McCafferty.
It is not just the English clubs who are up in arms over ERC's handling of the two high-profile tournaments.
Recent reports suggested French clubs have also threatened to withdraw.
The 'notice' by the English clubs may well force Europe's officialdom to return to the negotiation table.
The disagreement centres around a suggestion that the number of clubs in the Heineken Cup are reduced from 24 to 20.
Both Premiership Rugby and the French body (Ligue Nationale de Rugby) are against this reduction.
The suggestion has been that the top six clubs from the Premiership, the French Top 14 and the Pro12 (Celtic Nations plus Italy), plus the defending Heineken Cup champions and the Amlin Challenge Cup winners qualify for the competition.
According to a report in the Daily Telegraph, the another 18 clubs would play in the Challenge Cup, with the remaining two places in the second-tier competition filled by two clubs qualifying from a proposed third-tier competition - which would embrace countries such as Spain, Russia, Georgia and Portugal.
The English and French clubs are likely to meet strong resistance from the Pro12 teams (Ireland, Wales, Scotland and Italy) - who stand to lose most under the proposals.
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