Top luxury brands including Christian Dior, Dolce & Gabbana and Chanel are among the least transparent businesses when it comes to labour conditions in their supply chains, according to research released five years after the Rana Plaza disaster, the sector’s deadliest industrial accident on record.

Dior discloses virtually nothing about where its clothes are made, according to this year’s Fashion Transparency Index, while D&G, Chanel, Marc Jacobs, Versace and Giorgio Armani all scored less than 10pc of the total available points.

The report was published by Fashion Revolution, a campaign group set up after the collapse of Rana Plaza, a complex of garment factories in Bangladesh, which killed more than 1,100 workers.

It ranked companies based on how open they were about where their clothes were made, who was responsible for conditions in their supply chain and how they dealt with trade unions.