Premier blamed high commodity costs, which have knocked £15m from its profits, and the temporary loss of major customer Marks & Spencer when Premier raised its prices.
The maker of Hovis and Mr Kipling also said its grocery and bread markets have shrunk by five per cent, which it said was partly due to the unusually warm weather.
The FTSE 250-listed firm said trading profit in the first half will be between £65m and £70m when it reports in August, compared with £94m in the same period last year.
Premier, which was already offloading assets including the Quorn brand to tackle its debt pile, is also cutting its capital expenditure this year to mitigate the fall in trading. But it warned that the second half is also expected to be down year-on-year.