Ethical Trading Initiative, Fair Labor Association say they are backed by 17 international manufacturers, including Adidas, Gap, Tesco, H&M and Patagonia.
Garment factories threatening closure over proposed minimum wage adjustments could face legal action if they fail to obey official procedures.
The All-Myanmar Network of Trade Unions rejects the 3,600-kyat-a-day offer and calls on workers to be prepared to take to the streets in protest.
The Confederation of Trade Unions of Myanmar throws its support behind a government-led proposal for a minimum wage in Burma of 3,600 kyat (US$3.60) a day.
Foreign and domestic factory representatives say the proposed minimum wage is unaffordable.
Negotiations are currently being held in Rangoon which may pave the way for an official minimum wage in Burma.