Mike Phillips, James Hook, Gethin Jenkins, and Luke Charteris are among those to have already moved to France while Welsh starlets George North, Alex Cuthbert and Dan Lydiate are also believed to be targets for the top French sides.
The WRU had planned to fund central contracts for Warren Gatland's players by using the £6.2 million normally given to the regions for releasing them for international duty.
However Lewis says their proposed offer has been turned down by the Scarlets, the Ospreys, Cardiff Blues and Newport Gwent Dragons.
"That offer was not accepted by the regions," Lewis wrote in an open letter to Welsh rugby. "That is their contractual right and I respect it.
"The recent debate, if you can call it that, about player salaries and soundbite solutions has been untimely, misinformed and damaging.
"An important fact to the salary issue is that the WRU, on August 14 this year, formally offered to the four regions to centrally contract the entire international squad of players within Wales.
"It would have meant that the WRU would have managed players' salaries and careers, and directly we would negotiate with any player seeking to leave Wales.
"The £6.2m player release money would be retained by the WRU to fund this and the surplus, and yes there is a surplus, would be spent on nurturing new talent."
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