In February 2018 Ethical Consumer viewed The Conscious Consumer's website, mamoq.com, which listed clothing items made from leather, wool and silk. As a result the company lost half a mark under Ethical Consumer’s Animal Rights category.

With regards to leather the brand Issara was said have a "small, transparent supply chain." Mamoq's website stated that "They source hides from New Zealand, which is renowned for animal husbandry techniques and high animal welfare. The hides are tanned at a family-owned business in NZ before being shipped to Central Java and Eastern India where they are turned into Issara creations."
The brand Semura opts for vegetable-tanned leather that uses natural tannins found in the bark of trees.
There were several other brands which used leather - one was using scraps of leather and one was using natural leather. A shoe brand did not appear to have a policy on leather sourcing.
Leather, as the hide of a dead animal, naturally decomposes. To prevent this decomposition the leather industry uses a cocktail of harmful chemicals including trivalent chromium sulphate, sodium sulphide, sodium sulfhydrate, arsenic and cyanide to preserve it. Tannery effluent also contains large amounts of other pollutants, such as protein, hair, salt, lime sludge and acids. These can all pollute the land, air, and water supply making it a highly polluting industry.
Although some used vegetable tanning methods, the effluent from this still contains high levels of difficult to treat substances. As a result the company lost half a mark in the pollution and toxics category.

With regards to other animal derived materials. At the time of writing Mamoq did not appear to sell items of clothing made using down / feathers / angora or fur. However there was no policy to state that it would not ever sell products made from these items.

The company did retail products containing merino wool. In an communications with the company it stated "We ensure that all wool is Muelsing Free unless it is recycled / upcycled."

The company did retail products conatining silk. In communication with the company it stated "The only time silk worms are killed is when the silk comes from an end of roll materials eg: mayamiko which we still consider to be ethical as it is using materials that would otherwise be discarded."

Reference:

Best Buy Screening Questionnaire (7 February 2018)