The balls used at the World Cup are to be investigated following complaints from New Zealand fly-half Dan Carter.

Carter, who missed five out of nine place-kick attempts against Scotland, is unhappy the balls players have been given in practice are different from those used in the matches.

And Greg Thomas, the International Rugby Board's head of communications, admitted the tournament organisers have asked manufacturers Gilbert to examine Carter's comments.

"There should not be any difference between the balls given to teams for training and those used in matches," Thomas said.

"We have not had an official complaint from New Zealand but we are aware of Daniel Carter's observations and we have asked Gilbert to look into the matter. Their response was immediate and they are currently carrying out an inquiry."