(Updates shares in the second paragraph.)

Oct. 28 (Bloomberg) -- Aon Corp., the largest insurance broker, fell the most in 11 weeks as profit missed analysts’ estimates and margins declined at the consulting business.

Aon dropped $2.80, or 5.5 percent to $47.99 at 4:01 p.m. in New York trading. Operating profit of 69 cents per share at the Chicago-based company missed by 3 cents the average estimate of 18 analysts surveyed by Bloomberg.

The consulting services operation posted a 2 percent decline in so-called organic revenue, which excludes the impact of currency fluctuation and acquisitions. The decrease was fueled by a slump in health-and-benefits and communications consulting, the company said in a statement today. The adjusted operating margin at the HR Solutions division, which includes consulting, slipped to 11 percent from 17 percent.

“We’ve got to do better operationally,” Chief Executive Officer Gregory Case said in a conference call today with investors and analysts. “There was greater economic headwinds” in regions including Europe and the U.S.

--Editors: Dan Kraut, Steve Dickson

To contact the reporter on this story: Maryellen Tighe in New York at mtighe6@bloomberg.net

To contact the editor responsible for this story: Dan Kraut at dkraut2@bloomberg.net