An outbreak of bird flu is blamed for Bernard Matthews' woes
Brands owned by food producer Bernard Matthews plunged in value by £20m in 2008, a consultants' report claims.
The Norfolk and Suffolk-based firm has dropped 38 places to 98th in an annual chart of the top 100 UK grocery brands.
The table compiled by independent brand valuers analyses sales, market share, projected growth and customer loyalty.
Consultants Intangible Business said: "After bird flu and health scares it is perhaps no surprise Bernard Matthews brands would be affected negatively."
Three years ago TV chef Jamie Oliver singled out Bernard Matthews' Turkey Twizzlers for criticism in his campaign to feed children better food.
But a new lower-fat recipe helped boost the brand's sales.
In February 2007 a Bernard Matthews turkey farm in Suffolk was struck by the H5N1 strain of avian-influenza and thousands of birds died.
New marketing campaign
A spokesman for Bernard Matthews said: "The company has recently unveiled details of its business recovery plan and brand re-launch.
"Bernard Matthews Farms will focus on British turkey farming and production, making products that better meet the needs of today's consumers and championing British agriculture.
"The company recently launched its new £3m 'Proud to work at Bernard Matthews Farms' marketing and advertising campaign.
"This is aimed to communicate the company's farming heritage and support the launch of a series of new products."
Coca-Cola once again topped the annual chart of the 100 top food and drink brands in Britain, the consultants said.
The fastest mover in this year's chart was Kettle Chips, also based in Norfolk, which saw a 28% increase in brand value to rocket up the charts 20 places to 75th spot.