In a gloomy trading statement, Trinity Mirror said it had seen a marked decline in ad revenues over May and June, and that it expected conditions to remain tough for the rest of the year.
At 11am, shares in the company were trading at 113 pence, a fall of 25% or 38.3 pence.
For the nine weeks ending today, Trinity's advertising revenue was down by 12%. This included a fall of 6.5% at its UK nationals and 6% for its regionals.
In the trading statement, the company said volatility could worsen in a "very uncertain economic outlook" and that the company would continue to cut costs.
The statement added: "In the challenging advertising environment, management continues to manage the cost base tightly and will continue to seek opportunities for further efficiencies in operations."
It also said that a share buy-back scheme would be scaled down.
While the news was bad for its newspaper business, Trinity Mirror said that online revenues were up by 24.4%.
trinity mirror
Trinity Mirror profit warning sends shares tumbling
LONDON - Shares in Trinity Mirror Group lost almost a quarter of their value in trading this morning, after the publisher warned it would fall 10% short of its profit targets.