Key figures in the rugby union establishment have hit out in a growing power struggle over plans by top English and French clubs to form a breakaway tournament.

European Rugby Cup (ERC) chairman Jean-Pierre Lux and International Rugby Board (IRB) chief executive Brett Gosper both issued stark warnings on the proposal's potential impact on the game.

Lux used a newspaper column to warn that any attempt by the two nations' top clubs to set up their own money-spinning contest "would not only be detrimental to European rugby, but also to the world game."

Gosper entered the fray shortly afterwards, urging "all parties to get together and find a resolution because we obviously believe it is in the interests of rugby to have a strong European competition - it's good for the clubs and good for the unions."

The acrimonious dispute centres on proposals tabled last year by Premiership Rugby and French counterparts Ligue Nationale de Rugby that they could quit the Heineken Cup and the Amlin Challenge Cup when the current agreement expires in 2014.

Top clubs in England and France are seeking more control over revenues and changes to the number of teams and the qualification process.

But talks on a shake-up have not proceeded to their satisfaction, prompting the two leagues to up the ante and announce plans to set up their own tournament, which they say teams from other nations would be free to join.

A rattled Lux warned that the knock-on effect would "come back to shake the very foundations of the same English clubs who should be entering into genuine negotiations aimed at strengthening European club rugby.

"The core of this argument centres on the desire of Premiership Rugby, with the support of vocal club owners, to renege on a legitimate and commercially-sound TV contract - which was signed and approved by the board of ERC - in favour of a deal which they chose to progress outside the agreed ERC policy of central marketing."

To succeed the two-nation tournament plan would need to be ratified by the Rugby Football Union (RFU), the French Rugby Federation and IRB.

RFU chief executive Ian Ritchie called for peace talks, but said: "I don't minimise the difficulties - there are passionate, strongly-held views on all sides.

"I am ever the optimist," he added.