The following statement was released by both the Irish and Scottish Rugby Unions, after Tuesday's meeting of the Celtic League Association at London's Heathrow hotel.
"At a meeting of the Celtic League Association today, in London, the Welsh Rugby Union informed the Irish and Scottish Rugby Unions that the Welsh professional clubs have signed an agreement to participate in a new Anglo-Welsh Cup which results in five prime weekends in the season being unavailable for Celtic League.
"As a consequence, it has not been possible to construct a mutually acceptable Celtic League competition for season 2005-06.
"The Scottish and Irish Rugby Unions are disappointed that the Welsh Rugby Union did not consult its partners in the Celtic League prior to making commitments to the Anglo-Welsh Cup, given the serious negative consequences it has on the Celtic League.
"It is hoped that discussions may continue between the Irish, Scottish and Welsh Rugby Unions along with the Italian Rugby Federation to structure a new competition in the 2006/07 season which would incorporate four Irish teams, three Scottish teams, four Italian teams and four Welsh teams.
"In the meantime, for the 2005/06 season, Ireland and Scotland will structure a cross-border competition to commence in September 2005. It is proposed that this will be a 12-game, home and away league competition with qualification for Europe and a Cup competition, the details of which are to be finalised."
The Celtic League tournament came into existence on Friday, August 17, 2001. For two seasons previous to that, both Edinburgh and Glasgow had been competing in the rebranded "Welsh-Scottish League".
In 2002/03, Munster gained revenge when they powered past Neath 37-17 in front of 30,000 spectators at Cardiff's Millennium Stadium. The tournament followed the same pool and knock-out stages format, with a new Scottish side "The Borders" involved.
2003/04 saw a first Welsh victory as Llanelli Scarlets fended off the best second-placed Ulster could through at them to prevail in a newly-set-up play-off system - nine months of straight home-and-away competition.
Ulster, then coached by Alan Solomons, reigned supreme though in the first ever Celtic Cup competition, a mid-season knock-out spin-off from the league. The northerners beat Edinburgh 27-21 in the Murrayfield decider.
Last season, 2004/05, saw both Munster (second) and Leinster (third) push Welsh region The Ospreys hard over the same home-and-away league system.
Alan Gaffney's Munster side finished seven points behind the Neath-Swansea side, but ended their campaign on song - taking the Celtic Cup title, the last one of its ilk, against the Scarlets (27-16) at Lansdowne Road, in early May.
Connacht, who once again reached the European Challenge Cup semi-final, narrowly missed out on a place in the Heineken Cup qualification play-off - being edged for the highest non-qualifying spot in the league by three points, by the Cardiff Blues.