Sir Michael Perry, chairman, said: "Trading conditions are unlikely to alter materially during the balance of the year. In Europe, the underlying sales and margin performance of our consumer operations was disappointing at the start of the year, although there was some improvement as the period progressed."
Dealers seized on the company's cautious prognosis, clipping 21p off the share price, which closed at 1,259p. Analysts took the red pen to forecasts, which had ranged as high as pounds 2.7bn for the full year, cutting estimates to pounds 2.3bn-pounds 2.6bn.
Pre-tax profits at the half-way stage were 5 per cent higher at pounds 1.11bn. Earnings per share increased by a similar margin to 37.95p. The interim dividend will be announced with third-quarter figures in November.
Analysts described their meeting with the company as "downbeat" and suggested trading had been tougher than the company expected earlier in the year. Yellow fats, where Unilever's brands include Flora and Blue Band, continued to suffer from a decline in the overall market. The ongoing fall-out from the disastrous marketing flop, Persil Power, hit detergent profits.
Unilever's increasing caution follows similar shifts in expectations recently at a range of leading companies, including Wilson Bowden, the housebuilder, and Rexam, the former Bowater packaging business. The spread of businesses warning that profits growth is slowing has suggested a marked downturn in the economies of Europe and the US.
Operating profits increased in all three of Unilever's trading regions during the first half - Europe, which accounts for more than half group profits, increased from pounds 376m to pounds 385m, making up some of the shortfall in a poor first quarter, and North America and the rest of the world were both sharply higher.
Unilever has endured a year of unwelcome publicity. It pulled Persil Power after admitting that in some circumstances it could damage clothes. Recently a US Christian lobbying organisation accused the company of corrupting values in America by advertising during "depraved" television programmes such as NYPD Blue.