In July, French magistrates also opened an inquiry into allegations four fashion groups including Uniqlo and the owner of Zara profited from forced labour of the Uighur minority in China
Rights activists said on Monday they had filed a criminal complaint in Germany against five retailers including C&A, Lidl and Hugo Boss, accusing them of benefiting from forced labour among China's Uighur population.
The European Centre for Constitutional and Human Rights (ECCHR) said it had filed the case, which also targeted the two supermarket chains Aldi Nord and Aldi Sued, after carrying out an open-source investigation.
The ECCHR's Miriam Saage-Maass said it was difficult for civil society organisations to obtain clear evidence of the abuse but there was enough for prosecutors to take a closer look.
She said there was plenty of information emerging to suggest forced labour was taking place.
"The question is whether entertaining business relationships is not a way of aiding and abetting those international crimes," she said.
Saage-Maass added that the five companies had listed "publicly and voluntarily" their supplying factories from Xinjiang -- the Chinese province at the centre of forced-labour allegations -- but that they may just be the tip of the iceberg.
"We do believe that those five are really only an example of a much wider and more systematic problem," she said.
She pointed out that Chinese cotton made up 20% of global production -- and 80% of it was produced in Xinjiang.
"So, it's very likely that there are many more companies sourcing from the region," she added.
The United States says that Beijing is carrying out genocide against Uighurs and other mostly Muslim Turkic people in Xinjiang, where experts estimate more than one million people are incarcerated in camps.
Beijing denies genocide and has described the camps as vocational training centres, an assertion dismissed by Uighurs who say they are being forced to renounce religious traditions.
Several major consumer brands including Uniqlo, H&M, Nike and Adidas announced last year that they would stop buying cotton from the region, leading to boycott calls in China.
The ECCHR's move follows similar action in France.
In July, French magistrates opened an inquiry into allegations four fashion groups including Uniqlo and the owner of Zara profited from forced labour of the Uighur minority in China.
The case is based on a complaint lodged in April by the anti-corruption group Sherpa, the French branch of the Clean Clothes Campaign, and the Uighur Institute of Europe, as well as by a Uighur woman who had been held in a camp in Xinjiang, China.