Gareth Thomas has blamed player burnout for the decision by French clubs to opt out of next season's Heineken Cup.
Thomas has played in France for three years
The former Wales captain, a Heineken Cup winner with Toulouse, told BBC Sport on Five: "In France, and England, the top players play week in, week out.
"After three or four years of doing it, you can see on the training field that they are physically tired.
"The French League is very congested (in terms of fixtures), and the World Cup will just clog it up even more."
Thomas claimed players in France's elite league, the Top 14, face a seemingly never-ending schedule.
"They play for their country, in the league and Europe for their clubs, then it's the autumn internationals, more league, more European games, then the Six Nations," he said.
For the French, the league is more important than the Heineken Cup - it's a financial decision
"The next league season in France will start later because of the World Cup but ends at the same time - we will end up not having enough days in the week to play all our games."
Former Wales star Jonathan Davies says the home nations are facing a difficult decision after the announcement by French clubs.
He told BBC News 24: "All the other nations have got to look at themselves and ask is it a valued competition without the French clubs in it.
"I'm not sure what will happen, but it's a brave decision by the French."
BBC pundit Davies said the World Cup, which will be hosted by France this autumn, had forced its top clubs to make a tough choice.
"In every World Cup year, the fixture congestion is magnified and intensified, so basically they've looked at it and said one (competition) has got to go.
"For them, the league is more important than the Heineken Cup - it's a financial decision.
"A rugby decision would be for them to stay in it. But player burnout and a fixture congestion are always going to be a problem."