Thomas says English clubs are bound to Europe until 2009

The Rugby Football Union has warned the 12 teams after they voted not to play in the Heineken Cup if a planned boycott by French clubs goes ahead.

"They are legally bound to play in the Heineken Cup for the next two years," said RFU chairman Martyn Thomas.

"We would take action if Premier Rugby Limited tried to arrange alternative fixtures home or away without consent."

Interview: RFU chairman Martyn Thomas

Interview: Premier Rugby's Mark McCafferty

Interview: England's director of elite rugby Rob Andrew

The Premiership clubs agreed on Monday to withdraw from the European Cup or the European Shield if the elite French clubs go ahead with their threat to pull out.

606: DEBATE The entire relationship between the RFU and the clubs is an embarrassment CN

France's top clubs are protesting over voting rights and fixture congestion, caused by the Rugby World Cup which is hosted by France this autumn.

The English clubs are in dispute with the Rugby Football Union over shares and voting rights.

Thomas said he was "at a loss to understand" the clubs' decision to threaten a boycott, and warned them any resulting income loss would be their problem.

"The loss of revenue to PRL for their non-participation in the Heineken Cup will be theirs to absorb alone because the English income from the Heineken Cup is transferred, in its entirety, to the clubs by the RFU," he said.

"We have a contract with our clubs which we signed in 2001 and in relation to Europe it is very simple.

"It says the clubs will compete in the European Cup or the European Shield.

"That lasts until 2009 so I am at a loss to understand their statement that they believe they can pull out."

We will have to fill the fixture schedule now with new games in the Premiership or expanding the existing competition Premier League chief Mark McCafferty

The Ligue Nationale de Rugby, which represents the top 14 French sides, is likely to decide by Thursday whether or not to pull out of European competition next season.

Their decision will force the hand of their English counterparts, and Premier Rugby chief Mark McCafferty is not optimistic the French clubs will change their mind.

However, McCafferty is already working on contingency plans to fill weekends left blank by a lack of European action.

"I'm going to continue to find a way to pull the French clubs back in but the prospect of that doesn't look great," he told Five Live.

"We will have to fill the fixture schedule now with new games in the Premiership or expanding the existing competitions and Anglo-Welsh tournament.

"We also need to add European fixtures on a one-off basis until we can find a way forward."

But Thomas poured cold water on those plans, insisting any planned expansion would need RFU consent.

"I can't see a situation where we would countenance another competition when one is being damaged," said Thomas.