The regions have been in dispute with the WRU over a host of issues but failed to reach an agreement by Tuesday's deadline. They said it was impossible to plan for next season without the financial and fixture guarantees they need.
The Welsh regions have previously joined the French and English clubs in their plans for a breakaway European club competition, which has subsequently been thrown into disarray by the French clubs' u-turn and decision to stay with the Heineken Cup.
Tuesday's statement appears to now leave the Welsh regions and English clubs on their own, however, the format and structure for next season's European competition is still unclear.
"RRW and the Regions re-affirm their commitment to the Rugby Champions Cup under the aegis of Six Nations, which will generate a guaranteed 12 million pounds ($19.88 million)additional funding across the four regions over the next three years and help reduce the funding gap compared to the French, English, Irish and Scottish clubs," Regional Rugby Wales (RRW)said in a statement on Tuesday.
The Welsh regions have been struggling financially for many years and have seen many of their high profile players join English and French clubs - such as George North and Mike Phillips.
Despite the national team's success in the Six Nations in recent seasons and Wales' huge influence in the British and Irish Lions' series victory over Australia this year, the clubs have struggled desperately to make any impact in the Heineken Cup.
"It is astonishing that they (WRU) have put the four businesses in this position as a result of failing to fulfil their obligations under the agreement, despite having almost two years to resolve the issues involved," RRW added.
"As it stands, the Regions do not believe the participation agreement reflects the changes and demands of the modern game."
The WRU argued the regions knew what they had signed up for.
"The participation agreement provided a 10 year rugby framework for the professional game in Wales and is an integral part of the rugby pyramid structure in Wales," the WRU said.
"The decision of the existing regional organisations not to continue with the PA has now freed the WRU to present a new participation agreement focused on recognising and rewarding regions which identify, develop and retain players capable of challenging for international honours with Wales. This is in the best interests of Welsh rugby."
($1 = 0.6038 British pounds)