Trinity, which publishes the Daily Mirror and Sunday Mirror newspapers, has blamed the deteriorating advertising market for the poor results and has said the group expects the full-year operating profit to be 10% lower than expected.
In a statement to the stock exchange it said: "Since our Interim Management Statement covering the 17 weeks to 27 April 2008, advertising market conditions have deteriorated.
"We have seen a marked year-on-year decline in advertising revenues across our businesses during May and June and this is expected to continue for the remainder of the year."
National titles' advertising revenue dropped 6.5% year-on-year, while regional newspapers were down 6% in the same period.
Trinity is now cancelling the remaining £67m of its share buyback programme in order to save money. The company had planned to buy back £175m worth of shares from the stock exchange. So far 35.5m shares have been bought, at a cost of £108m.
Trinity Mirror warns of declining profits
One of the country's largest newspaper publishers, Trinity Mirror, has today issued a profit warning ahead of its half-year interim results due at the end of July.