Rugby Players Association chief executive Damian Hopley fears the prospect of an exodus of top English internationals to French clubs.
England recently declared they would only select overseas-based players in "exceptional circumstances" after next year's World Cup.
"We want the best players playing in England and we want the best English players playing in England," said Hopley.
However, Jonny Wilkinson indicated on Monday that he will extend his stay in Toulon while Sale are expecting Andrew Sheridan to join him at the end of the season.
Some of England's most exciting prospects such as Ben Foden, Courtney Lawes and Chris Ashton are also reported to have attracted interest from across the Channel.
Hopley backs the Rugby Football Union's position and has warned RPA's members that they must face the consequences if they do leave the Aviva Premiership.
"There is clearly a concern that there might be an exodus of the best English players after the next World Cup. We want the best English players playing in England for the next two World Cups," he said.
"The announcement by England was a bit heavy-handed but we believe it will force players to make a decision sooner rather than later. If this is what it takes to get the best results from England at the 2015 World Cup, then that's the price players will have to pay.
"They know they can go to France and get a guaranteed amount of money or they can fight for their place in England.
"Hopefully the profile of the game will continue to rise and that will make up for what they might earn in France."