Wren signed off the group's results with Randall Weisenburger, the group's chief financial officer. Both were under intense pressure as investors demanded answers following questions raised about its accounting methods back in June.
The Securities & Exchanges Commission has required the country's 947 largest public companies to affirm their SEC filings for the year, in the wake of the Enron and WorldCom scandals.
Wren said: "We are pleased to sign these certificates to evidence our continuing commitment to integrity in financial reporting."
In June, Omnicom's share priced collapsed after a story on the front page of the Wall Street Journal questioned the company's accounting, especially the way it had handled its internet assets. This sparked a slew of class action lawsuits. However, Omnicom's auditor KPMG said on August 6 that it was not advising its client to change the way it accounts for its internet businesses.
Shares in Omnicom were down by 2.02% in New York this morning, trading at $51.31.
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the .