The Rugby Football Union's elite rugby director Rob Andrew has warned players who take up lucrative club contracts abroad risk jeopardising their international careers.
Wasps trio James Haskell, Riki Flutey and Tom Palmer have all agreed summer moves to the French championship and there are fears of a further exodus across the Channel.
Haskell and Flutey are reported to have nearly trebled their wages at Stade Francais and Brive respectively by virtue of an attractive rate of exchange between the pound and the euro - and the fact Top 14 clubs are not hindered by a salary cap.
England team manager Martin Johnson told all three players that moving outside of the Guinness Premiership - and therefore England's £100million elite player agreement - makes it much harder for their form and fitness to be judged.
Haskell insisted moving to France would not affect his England career because his contract with Stade contains a clause making him available for all national training sessions, including those that fall outside of the official international window.
But the RFU is still trying to discover exactly how detailed that release agreement is - and Andrew spelled out the severe implications facing any player who is not available for every England training session.
"The key thing is the integrity of the England team and Martin's ability to have the players when he wants them for preparation, which is clearly a massive part of the EPS (elite player squad) agreement," said Andrew.
"These players (who are moving abroad) will need to be available when Martin wants them available because, by definition, if they are not that will compromise their own situation.
"There are two things that will clearly impact on a player playing for England - one is form and the second is whether he is available when the team preparations are going on.
"What we effectively did with the EPS agreement was buy more preparation time. Players would have to make sure they have that covered in their individual contracts.
"We need to get the exact detail of what their contracts actually say so we can understand the whole picture."
Even if Haskell, Flutey and Palmer are able to make every national training session, their move to France is set to deny England the ability to closely monitor their fitness and form.
Although Johnson did select Brive's Andy Goode for England's first two RBS 6 Nations games after watching his performances on DVD, the impact of having increasing numbers based outside the elite player squad agreement is wide-reaching.
Andrew explained: "There are quite a lot of things that need to be considered in this.
"It is not just training times (that are outlined in the EPS agreement) but the medical profiling which we do with every player each week, the August training camp, the fact the players have to be guaranteed a rest one week in five and there is a limit on the number of games they can play in a season."
Johnson met with Haskell, Palmer and Flutey in the early stages of their contract discussion and urged them to ensure a clear England release agreement was included in the deal for the sake of their international futures.
"The guys have all said they want to play for England," said Johnson. "They don't want this to affect them playing for England and how do they go about that happening?
"I said to them that if they go out of England they need to get the release taken care of otherwise it makes it very difficult. If they don't have that it will make it more difficult."
Johnson addressed the whole issue with the England squad and encouraged any other players considering a move abroad to consult him for advice.
"We will not tell them what to do. They are professional players who have a short career and ultimately it is their call but we will give them advice, or strong advice in some cases," he added.
"We explained to them that it does make it more difficult for us to see them play. We can watch the tapes but they are not competing in the Premiership. We can't compare them week-in and week-out.
"My advice to the players usually is to do what is best for your rugby career. They know the implications of what might happen to their form and their chances of playing for England."
Andrew, who spent a year playing for Toulouse after the 1991 World Cup, insisted the RFU was not considering the drastic measure of insisting only Guinness Premiership players were available for England.