ERC is not entitled after 2014 to sell the broadcast rights
England's Premiership clubs and European officials were on a collision course over the validity of a new £152 million (US$245 million) domestic television deal.
The four-year contract, which starts next season, will see BT Vision as the only platform on which to watch top-flight English club rugby.
However, continental rugby chiefs say a clause granting that company exclusive live broadcast rights to matches played by Premiership clubs in any future European competitions from 2014-15 for three years is invalid.
In a statement issued following a board meeting at its Dublin headquarters on Wednesday, European Rugby Cup (ERC) said the "purported deal" was in breach both of International Rugby Board (IRB) regulations and an ERC board mandate.
The statement said it was "unanimously agreed" at an ERC board meeting on June 6 that ERC would conclude a new four-year agreement with another satellite broadcaster for the UK and Ireland exclusive live broadcast rights to the European Cup and the European Challenge Cup until 2018.
It added: "Premiership Rugby was party to that decision".
However, Premiership Rugby, the umbrella body for England's 12 top-flight clubs, hit back with a strongly worded statement of their own insisting they had not entered into any binding agreement with ERC.
"ERC and its board acknowledged and accepted that notice was served on the ERC accord on June 1 by Premiership Rugby and [France's] Ligue Nationale de Rugby which means the Accord comes to an end in 2014," the statement said.
"Sky Sports have been made fully aware of this.
"As a result of notice being served, ERC is not entitled after 2014 to sell the broadcast rights of matches involving Premiership Rugby clubs."
As for the June 6 meeting, Premiership Rugby said: "No specific broadcast deal was presented or voted on at this or any subsequent ERC board meeting.
"ERC's suggestion that Premiership Rugby may be in breach of IRB regulations is wrong...When any future European competition launches in 2014, BT will have exclusive rights to broadcast the matches played by Premiership Rugby clubs."
A meeting involving the ERC and the clubs to discuss the future format of European tournaments after the existing agreement expires at the end of next season is due to take place in Dublin on Tuesday.
English and French teams are currently in dispute with ERC and are threatening a break-away competition.
French clubs have put forward a proposal for a European Cup reduced from the current 24 teams to 20 based on six from England, six from France and six from the Celtic League, as well as the reigning champions and the winners of the second tier European Challenge Cup.
The Celtic League element is controversial as it could lead to a European Cup without guaranteed representation from Scotland, Ireland, Wales and Italy, as happens at present.
Unlike the Premiership and France's top 14, there is no relegation from the Celtic League.
English and French clubs have long believed this gives Irish provinces in particular an unfair advantage, as they can rest players from domestic duty ahead of European Cup ties without much fear of the consequences.
Between them Munster and Leinster have won four out of the last five European Cups, with Leinster beating Irish rivals Ulster in last season's final as they lifted the trophy for the third time.