Primark, Tesco, Asda and Marks & Spencer are among a raft of retailers who have written to the Cambodian prime minister demanding an investigation into the “deadly force” used on factory workers striking over minimum wage.

Retailers including Debenhams, Next, Gap, Zara, New Look, Levi Strauss, Adidas, Nike, H&M and Walmart have written an open letter to prime minister Hun Sen demanding that they meet so they can express their “grave concern” at the killing and wounding of workers and bystanders at a recent protest by garment factory workers.

Signed by 30 retailers, the letter calls for the Cambodian government to launch an investigation into the incident and hold officers accountable, while it also urges the government to review its minimum wage.

The retailers also warned that business might be pulled out of the country if there were further incidents.

At least three people died at the beginning of January when military police opened fire on protestors in the capital Phnom Penh, at an industrial park making clothes for export to the west. It came after workers defied government orders to end their strike against low wages.  

Workers are calling for an increase to the industry’s minimum wage to $160 a month, up from the government’s latest offer of $100.  

Unions and activists say a living wage for garment workers would be $283 a month.

The other signatories of the letter are American Eagle, Bonmarche, C&A, Esprit, Fifth Pacific, Lululemon, Migros, N Brown, New Balance, Orsay, Puma, PVH, Tchibo, The Jones Group, Walt Disney, Under Armour.

The general secretaries of the International Trade Union Confederation and IndustriALL unions also signed the letter.