The decision was announced by club president Pierre Martinet who admitted it was Saint-Andre's apparent desire to take on the Wales job that made up his mind.
"You don't just dump your colleagues to go to Wales," said Martinet at a press conference. "It's really the last straw that broke the camel's back."
He made it clear he would not be dismissing Seigne who is a close friend of Saint-Andre and who, it is believed, could also be part of any management team with Wales.
Martinet said: "Our coach Laurent Seigne has a contract that runs until the end of next season - Laurent Seigne has no reason to leave the club."
Saint-Andre said: "I heard what he (Martinet) said. I have not heard anything like that before.
"A club and a team are more important than any one individual. Sometimes a coach or a director gets sacked for bad results. That is not the case here.
"I have always said we have great players, a great team. I have nothing else to add."