Pontypridd RFC are unhappy that Welsh Premiership teams are set to be replaced by regional 'A' sides in next season's British & Irish Cup.
The Welsh Rugby Union confirmed that: "The plan under discussion is to introduce Regional Premiership Select teams to the competition in future."
Ponty reached the quarter-finals this season and are twice semi-finalists.
"We're not going to sit down and take it," Pontypridd CEO Stephen Reardon said.
"We're going to make a fight of it and are willing to go all the way on it.
'We've dominated elite rugby for the last 5 years in Wales and our reward is to be denied by the regions."
No date has yet been set for when a final decision will be made on Wales' entrants for the British & Irish Cup in future seasons.
A statement from Reardon, said the club "vehemently rejects the proposal".
"In most sports, successful teams receive some sort of reward based upon meritocracy and achievement," read the statement on the Pontypridd website.
"In Pontypridd RFC's case it seems that its fate for being the most consistent and successful team in 'Elite Rugby' in Wales over the last five years, is that it is destined to be denied the opportunity to compete for qualification in the pool stages of the British & Irish Cup in the 2015/16 season.
"Pontypridd RFC vehemently rejects the proposal to remove the opportunity for Premier Division clubs to participate in the only cross-border competition for which they are eligible.
"Pontypridd RFC remains open to dialogue, but should negotiation fail it will use all the means at its disposal including the resolutions carried at tonight's [Tuesday's] Annual General Meeting of Ponty Rugby Limited to oppose the usurping of the British & Irish Cup by the regions."
Wales' representatives have come from the semi-pro Welsh Premiership since the competition's launch in 2009-10, competing against teams from the English Championship and 'A' sides from the Irish provincial teams.
As well as Ponty reaching the semis in 2011 and 2014, Llanelli made the quarters in 2013 and Cross Keys the final in 2012.
The WRU says the proposed change is part of a strategic review of the elite rugby competition structure, adding that a Competition Pathway Working Group started the review in March 2015.
"One element of the review is participation in the British and Irish Cup competition going forward and how this could also complement and underpin future participation in what was the LV=Cup," the WRU said in a statement.
"The plan under discussion is to introduce Regional Premiership Select teams to the competition in future, with an input from Regional coaching structures and selection from across the semi-professional clubs within each of the four regions.
"Any proposal would need to integrate the Premiership and regional squads to maximise the development potential for talented players and coaches across Wales.
"The declared ultimate aim of the WRU is to ensure that through the best available competition structures, the player pathway must continue to develop the very best talent for potential international selection."
Pontypridd fall under Cardiff Blues' umbrella of influence and a statement is expected on Wednesday from the regional side.
Ospreys, Scarlets and Newport Gwent Dragons are the three other professional Welsh regions.
Pontypridd did the double of winning the Welsh Premiership and Welsh Cup in 2013 and 2014.
The Sardis Road side reached the final of the Cup this season and again topped the league table this season to earn home advantage in the play-offs - where they face Ebbw Vale in the final on Sunday, 17 May.