That cup competition is understood to be more lucrative to Welsh clubs than participation in the Magners League, but at yesterday's launch of the 2008-9 competition at the Royal Dublin Society Showground, home to reigning Magners champions Leinster, it was underlined that the Welsh, Irish and Scottish rugby unions had signed up to a longer Celtic season with play-offs from next summer in a concerted bid to strengthen Celtic rugby, without interference from other tournaments.

David Jordan, the Celtic League's chief executive, stated: "The three Celtic unions have agreed guiding principles – a play-off of the top four teams to determine the winners, which gives us a 20-week competition; all teams will play on the same weekend, so, in other words, no other competitions can take place on Magners League weekends (ie: EDF Cup].

"We will not play in the week before the autumn Test window and the week before the RBS Six Nations Championship, to allow international squads chance to prepare, and obviously we will not clash with Heineken Cup and European Challenge Cup weekends.

"I don't know anything about the EDF Cup plans, but the Welsh are with us on this. There may be scope for them to play their cup during the international breaks, but that doesn't concern us."

The EDF Cup agreement between English and Welsh clubs ends next year, which is why the Magners League have waited until now to agree a new format. The new structure will create the scenario of a team finishing top of the pile after the 18 rounds of games, but, potentially, not being crowned champions through failing to win the play-offs – common in the major competitions, such as the Guinness Premiership, Super 14 and French Top 14.

Robinson, Edinburgh's head coach, believes it would enhance the prospects of success for the pro teams and Scotland through enabling proper rest for leading players.

He said: "I think play-offs are a good thing. You need a big squad if you want quality rugby and to really compete in the Heineken Cup and Magners League, and Scotland in internationals. Every player can't play each week, but having play-offs at the end gives you more confidence to give a player a week off and potentially limit injuries."

Glasgow coach Lineen is hopeful that play-offs will lift the Magners League to an even greater level.

"Every major competition has moved to play-offs and I think this brings credibility to our league," he said.