Shares in ITV fell more than 5 percent this morning after the broadcaster acknowledged that its advertising revenue had started to decline in the final stages of the year.
ITV has blamed the "increasingly unsafe environment" for advertising revenues to decline by around 3 percent in the fourth quarter and remain broadly flat for the year.
As advertising cash weakened in the final quarter, advertising revenues rose 2 percent in the first nine months of the year, and online revenue grew 43 percent.
Falling: ITV shares fell more than 4 percent this morning
ITV's FTSE 100 share price fell 5.3 percent or 8.17 pence to 146 pence.
In my hometown I am a star, Coronation Street and the X-Factor. In recent years, ITV has rebuilt itself to reduce reliance on volatile advertising by building its studio production division.
The FTSE 100 listed company saw a 6% increase in external revenues to £ 2.257 billion (£ 2.139 billion in the previous year), with continued growth in all businesses.
Prior to today's trading update, analysts warned that the lack of political agreement on Britain's exit from the European Union in less than five months could deter major brands from spending on major advertising campaigns.
Citi said the trade update was as expected and "a relief given the uncertainty". It rates the station as a "buy share".
David Madden, an analyst at CMC Markets, said: "The uncertainty surrounding Brexit has been blamed for the cautious outlook, and it is reasonable that large companies could curtail advertising before the UK leaves the EU, especially as there is no retreat agreed.
"The group has stepped up its video-on-demand business to compete with Netflix and Amazon Prime. The online platforms will offer more ad space as the ITV hub becomes more popular. "
Advertising sales: ITV expects its advertising revenues to decline by around 3 percent in the fourth quarter
Roddy Davidson, an analyst at Shore Capital, said: "We are encouraged by the positive development of the first nine months of the year and the prospects for studios and digital advertising.
"It is disappointing to note the expectation of a weaker third quarter, but perhaps not entirely surprising given the high political / economic uncertainty surrounding the Brexit."
ITV reported strong first-half results in July, with the Football World Cup and reality show Love Island raising their share of the total viewing to a 10-year high.
Looking ahead, ITV head Carolyn McCall said: "We are very focused on implementing our strategy to create a stronger, more structurally sound business based on our strong operational performance in the areas of business we control build & #. 39; & # 39;