The controversial online search advertising deal between Google and Yahoo has received yet more opposition from a national trade body.

In a letter to North American and European competition regulators the World Association of Newspapers (WAN) said that the deal would have far-reaching, negative effects on the newspaper industry.

When the Yahoo-Google deal was struck in June the firms said that the tie-up would be of benefit to both parties and to their customers. Many industry members, however, have disagreed.

Last week the Association of National Advertisers expressed its opposition in a letter to the US Department of Justice, and now the France-based WAN has expressed concerns about the competitive elements of the deal.

WAN warned that Google and Yahoo already dominate the advertising market available to the newspaper industry, and explained that it felt that such a tie-up would affect it in three ways: less competition in the market, higher prices, and less revenues.

"WAN believes that the competition that currently exists between Google and Yahoo is absolutely essential to ensuring that our member titles receive competitive returns for online advertising on their sites, and for obtaining competitive prices when they purchase paid search advertising," the organisation said.

"In our view, the proposed advertising deal between Google and Yahoo would seriously weaken that competition, resulting in less revenues and higher prices for our members."

WAN said that regulators should block such a deal, and urged that Yahoo continue to be Google's main competitor in the online advertising industry.