Derbyshire-based Thorntons said its third quarter sales fell 7.6% over the 15 weeks to April 26, because of slower supermarket sales in February and March as well as the impact of store closures.
Shares tumbled 15%, even though it said sales of its seasonal specialities grew by more than 20% in a strong Easter performance.
Thorntons, which has suffered several profits warnings in recent years, is in the middle of a turnaround plan that involves cutting its portfolio of high street stores and selling more products through major supermarkets.
During the period the business said its supermarket sales fell 8%, partly due to a poor performance in the run up to Valentine's Day and Mother's Day.
The firm also saw sales at its own high street stores slip 8.8%, reflecting the 38 shops the company had closed during the previous year. Thorntons now has an estate of 271 stores.
Chief executive Jonathan Hart said: "Despite this third quarter result we are satisfied with the overall performance of the business for the year to date."
The company added that it expected to meet its market forecasts for the full year. Analysts forecast the business will turn in a 2014 pre-tax profit of £7.3 million.
The business did see a 5.7% increase in sales at franchise shops, a 5.6% rise in online sales, and a 1.2% like-for-like sales boost at its own stores that have been open for longer than a year.
Analysts at N+1 Singer said that even though the Thorntons update contained both negative and positive news they concluded "that the strategic actions being implemented are having the desired effect".