• by Karlene Lukovitz  @KLmarketdaily, January 28, 2011

Taco Bell isn't sitting still in the face of the class-action suit filed against the chain last week in federal court in California, alleging that the chain is falsely advertising ground beef when its fillings contain less than 35% beef. In addition to considering a countersuit, the QSR has launched a campaign in major newspapers with the bold headline: "Thank you for suing us. Here's the truth about our seasoned beef."

A quick, aggressive response would appear to be a smart strategic move, given that the chain's perception among fast-food diners has dropped considerably, according to YouGov BrandIndex.

In the week since the lawsuit was filed on Jan. 19, Taco Bell's overall BrandIndex perception score among adults 18+ who have eaten in a fast-food restaurant at least once during the past three months has fallen fast from 25.2 to 11.7. That puts the QSR below the average index score for the fast-food industry as a whole, which currently stands at 12.2.

BrandIndex's scores range from 100 to -100 and are compiled by subtracting negative online/social media feedback from positive feedback. A zero score means equal positive and negative feedback. The Index score is an overall brand-health metric that averages sub-scores of quality, value, satisfaction, reputation, willingness to recommend, and general impression.

BrandIndex interviews 5,000 people each weekday from a representative U.S. population sample. Respondents are drawn from an online panel of more than 1.5 million. The margin of error is +/- 2%.