Test centre Mark Gasnier says he has been forced out of rugby league because his NRL contract has not been fully honoured.

The St George Illawarra captain on Tuesday confirmed he would leave the Dragons at the end of the season to join French rugby union club Stade Francais on a two-year deal, ending months of speculation on his future.

While stressing his move was not motivated by money, Gasnier revealed an exit clause in his contract was only activated because he was owed third-party sponsorship money promised to him when he signed a five-year deal in 2006.

Dragons chief executive Peter Doust would not identify the third parties responsible but said: "It's fair to say those commitments have not been fulfilled."

Gasnier said he would not have looked at an offer from rugby union had his contract been honoured, but he had no choice but to leave because he felt like he was only earning "two-thirds" of his wages.

"The hardest things was to walk away from the club, I love the club," said Gasnier, who will earn an expected $1 million a year in rugby union.

"I grew up here, there's a lot of family history.

"But it's the circumstances that led me here.

"It's unfortunate how things come about but I've had to react to it and I think this is the best reaction for me."

Gasnier, who will link up with former Waratahs coach Ewan McKenzie in France, will stay on as Dragons captain for the rest of the season.

He will join Penrith premiership-winners Craig Gower and Luke Rooney in playing French rugby next season.

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