ACNielsen found that in the week to March 19 - a month after the scandal broke - year-on-year sales of Worcester sauce were down 9.7%.
This was the fourth and biggest consecutive fall in as many weeks.
For the two weeks leading up to that date, snack pots were also suffering with sales running 30% lower than a year ago, adding to the misery caused by an immediate 19.6% hit after the initial scare.
Chilled ready meals, previously in growth, have also been badly hit with no sign of customer confidence returning.
Since the February 18 nationwide recall of hundreds of lines containing contaminated Worcester sauce produced by Premier Foods, year-on-year sales fell by more than 5%.
Sales of frozen ready meals, already in decline, nosedived in February and March. Year-on-year sales of seafood sauce, intially hit hard, are still down by over 30%.
Sales of fresh pasta and fresh sauces, which initially appeared to escape, began a downward trend in the latter two weeks.
ACNielsen said it would keep monitoring the situation. The crisis was initially caused by chilli powder in Premier Foods’ Worcester sauce, contaminated with the illegal food dye.