The market has seen significant rises in ad revenue so far this year. Although the ad market was up 15%in the first half, media agencies expect the back end of the year to show less of a rise year on year against the improving second half of 2009.
Media agencies now expect TV revenues to rise by between 11% and 12% for 2010 as a whole. One head of trading said: "There is going to be a strong end to the year. I didn't believe it would happen but the year is looking like it will be up about 12%."
Channel 4 is expected to outperform the market in September, which is in part a reflection of media agencies fulfilling the share deals that were disrupted by over-spending on ITV during the World Cup.
ITV outperformed the ad market in the first half of the year and reported a net ad revenue rise of 18% or £728m in the six months to 30 June, but is expected to be closer to the market average of 15% in September.
ITV and Channel 4 declined to comment.