The BHRRC has been tracking allegations of workers' rights abuses in garment factories since the military junta took power in Myanmar, plunging it into political and humanitarian crisis.
There have been 21 cases of alleged abuses linked to Inditex suppliers over the two-year period, and 20 linked to H&M suppliers, according to the report.
The Myanmar Garment Manufacturing Association did not reply to a request for comment.
It expects its final orders from Myanmar suppliers to ship before the end of this year, but has also increased its presence on the ground.
H&M and Bestseller are among 18 brands that are part of the European Union-funded MADE project aimed at improving labour conditions in Myanmar's garment factories.
Persons:
Inditex, Spencer, Primark, we've, Karina Ufert, Vicky Bowman, Bowman, Helen Reid, Vanessa O'Connell, Marguerita Choy, Emelia
Organizations:
Reuters, Zara, Human Rights Resource, Myanmar Labour News, Myanmar Garment Manufacturing Association, Ethical Trade, European Union, European Chamber of Commerce, Myanmar Centre, Responsible Business, Thomson
Locations:
Myanmar, British, MYANMAR Spanish, Danish