LONDON, United Kingdom — Louis Vuitton is losing ground as the world's most valuable luxury brand as competitors including Gucci and Prada gain, a new research report shows.

Vuitton’s brand value declined 12 percent from a year ago to $22.7 billion, Millward Brown Optimor estimated in its 2013 BrandZ study. While the bagmaker owned by LVMH Moet Hennessy Louis Vuitton SA remains the most valuable luxury brand for an eighth straight year, rivals are better managing the trade-off between exclusivity and affordability, according to the report.

The value of PPR SA’s Gucci’s brand surged 48 percent to $12.7 billion, ranking it the third in the luxury list, while Prada’s worth soared 63 percent to $9.45 billion, placing it fourth, Millward Brown Optimor said. Hermès stayed in second place at $19.1 billion, unchanged from last year.

As consumers make “room for those luxuries that make them feel better by trading down on other items, it is the middle-of- the-road brands that are feeling the impact of this polarisation,” Millward Brown Optimor said in a statement.

Rolex, Chanel, Cartier, Burberry, Fendi and Coach rounded out the top 10 most valuable luxury brands in the study. Prada's surge was the fastest across 13 categories measured by Millward Brown Optimor, placing it 95th out of 100 brands overall. Apple Inc. again ranked first with its estimated value rising 1 percent to $185 billion, the study found.

“Prada’s brand awareness in China, Russia, Brazil and the Middle East continues to rise,” said Anastasia Kourovskaia, vice-president of Millward Brown Optimor EMEA.

The study, commissioned by WPP Plc, was based on interviews with consumers as well as analysis of company performance.

By: Andrew Roberts; Editors: Paul Jarvis, Robert Valpuesta.