The IAA said it raised concerns about the tie-up with the US Department of Justice back in August because it believed the deal could result in less competition, which might impact innovation.
Michael Lee, executive director of the IAA, said: "We don't know all the specifics of the transaction.
"However, concerns revolve around the ultimate probability of less competition, an increased pricing landscape, and the fear that such a monopoly could impact innovation.
"In principle and in practice, monopolistic media control and pricing has not been good for the industry."
The partnership between and , announced in June, sees the two search engine giants combine their search advertising systems, which will allow Google to sell advertising on Yahoo! in return for a share of the profits.
Google said last week that it was forging ahead with the partnership next month despite the investigations being carried out by the US Department of Justice and the European Union Competition Commission.
The IAA said it will continue to monitor the partnership and may conduct a global research study of the issues.