Star second row Matfield is joining ambitious French club Toulon

That means a number of stars, including captain John Smit and second row Victor Matfield, will play their last games for South Africa at the World Cup.

The South African Rugby Union (Saru) says it is trying to stem a flood of players to the northern hemisphere.

"It's a really tricky situation, but we had to draw the line somewhere," said Saru president Oregan Hoskins.

Hoskins, who was speaking to the Johannesburg-based Star newspaper, added: "We want to reward the guys who stay in South Africa and further encourage them to remain here."

Other Springboks who are heading north include wing Ashwin Willemse, utility back Brent Russell, number eight Bobby Skinstad, full-back Percy Montgomery, fly-half Butch James and hooker Gary Botha.

We're now simply reverting back to what the rule was Saru chief Oregan Hoskins

South Africa's fellow southern hemisphere giants New Zealand and Australia have similar policies of not picking players who play abroad.

Up to 100 South Africa-born players, including a number of former Test players, ply their trade in France, Wales, England and Italy.

In recent times Springbok coach Jake White has selected overseas-based players for the national team, most notably Montgomery and fly-half Jaco van der Westhuyzen.

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Saracens prop Cobus Visagie was also called up during the Tri-Nations series.

Hoskins said the authorities made an exception in those cases because White wanted to be able to pick those specific players.

"We're now simply reverting back to what the rule was and that means if a guy doesn't play locally he won't be allowed to play for South Africa," he said.

"If we allow guys to keep on leaving (South Africa) we'll also be robbing the public of seeing the best players in action."

The World Cup starts in France on 7 September, with the final in Paris on 20 October.