Some of Europe’s biggest stores are failing to stem the abuse of Syrian refugees who work in the Turkish factories that supply their clothes, a business pressure group said on Friday.

The Business and Human Rights Resource Centre (BHRRC) called on the worst offenders - from fashion icon Topshop to discounter Aldi - to better protect refugee workers who have fled war only to suffer workplace exploitation in their new home.

Low wages, discrimination and poor conditions are common for Syrian refugees working in Turkey’s multi-billion dollar garment industry, where child labor is also a problem, said the BHRRC.

“Some high street fashion brands ... have made progress in protecting workers, but too many, like Aldi, Asda and Topshop, are lagging way behind,” Phil Bloomer, executive director of the BHRRC, said in a statement.

“They should learn from the leaders, and quickly.”

The Britain-based charity surveyed 37 major European brands with Turkish factories in their supply chains on the policies and practices undertaken to tackle the abuse of workers.

Companies including supermarket chains Aldi and Asda and fashion retailer Arcadia - which owns the Topshop, Dorothy Perkins and Miss Selfridge brands - are not doing enough to stop the exploitation, the BHRRC survey found.

ASOS, New Look, Next, SuperDry and Zara were the top ranking brands in the survey; Asda and Arcadia came bottom. Six companies, including Mexx and River Island, failed to respond.

The charity said more brands had boosted efforts to clean up their supply chains compared to last year, with the top performers establishing plans to protect refugees, mechanisms to handle complaints, and initiating dialogue with workers’ groups.

More than 3 million Syrian refugees - about half aged under 18 - have fled to Turkey to escape a war that erupted in 2011.

About 650,000 are estimated to be working in Turkey, many in the garment industry, yet most lack work permits, leaving them at greater risk of abuse, the BHRRC said.

A Reuters investigation last year found evidence of Syrian refugee children in Turkey working in clothes factories in illegal conditions. Turkey bans children under 15 from working.

“The Syrian refugee crisis poses a complex challenge for retailers sourcing garments from Turkey,” said Peter McAllister, head of the Ethical Trading Initiative, an alliance of trade unions, firms and charities promoting workers’ rights.

“Refugees are particularly vulnerable to exploitation,” he told the Thomson Reuters Foundation. “More needs to be done, but we are confident our member companies are taking it seriously.”

A spokesman for Walmart, which owns Asda, said the company was exploring how to address the risks to vulnerable workers in its global supply chain, with a focus on ethical recruitment.

Topshop declined to comment on the BHRRC survey, Aldi did not immediately respond to requests for comment, and Mexx and River Island could not be reached.