Despite suffering a 3% fall in October, the broadcaster said it continues to outperform the overall TV advertising market.
The drop in spend has taken 12% off ITV's TV ad revenues for the first nine months of the year, leaving its total at £1.05bn.
Over the same period ITV's group revenues dropped 10.8%, coming in at £1.31bn compared with £1.47bn in the same period last year.
The broadcaster's family of channels suffered a drop in its share of commercial impacts (SOCI) from 40.9% to 39.5%, but ITV1 has extended its lead over BBC One in peaktime viewing.
There was no growth in production revenues, which stayed flat at £405m.
Despite executive chairman Michael Grade's push to increase the number of commissions for ITV's channels won by its content division, internal revenues fell 12%, counterbalancing growth in external revenues.
In online, ITV.com is now pulling in eight million average monthly unique users, up from 5.9 million last year. Revenues are up 45% to £16m, which equates to one hundredth of the company's overall income.
John Cresswell, chief operating officer at ITV, said: "While our visibility is limited, the outlook for the fourth quarter has continued to improve and ITV is continuing to outperform the market.
"With further cost savings and a strong schedule in 2010, including the World Cup, we are confident that ITV is well-positioned to benefit from any market recovery."