Add another voice to the growing chorus of opposition to Google's proposed search deal with Yahoo. The World Federation of Advertisers (WFA), which says it speaks for 55 national advertiser associations around the globe, is asking the European Commission to block the agreement.

While the proposed tie-up, which Google said will proceed in October, only impacts North American websites, the WFA has taken an interest because of concerns that approval in the U.S. would make an eventual wider deal something of a fait accompli.  

"The substantial benefits for both parties in the U.S. and Canada will almost certainly reduce their incentive to compete in other markets as they do today," the WFA said in a statement.