The United Nations human rights envoy in Cambodia has called for a "proper mechanism" for setting minimum wages in the country.

In a statement issued at the end of an official visit to Cambodia this week, Professor Surya Subedi expressed his concern at the inability to set a minimum wage that meets workers' expectations, reflects the rising cost of living and is regularly reviewed.

"I urge the government to negotiate with workers and their representatives in the garment sector in good faith and to seek international assistance, such as from the International Labour Organization (ILO), toward the establishment of a proper minimum wage determination mechanism," he said.

Cambodian unions and garment workers want the minimum wage to be doubled from US$80 to $160 immediately, whereas the Labour Advisory Committee has proposed an initial increase to US$95 per month from 1 April, with incremental rises to $160 over the next five years.

The calls follow a two-week garment worker strike which ended last week, and protests which resulted in the deaths of at least four people when military police opened fire on protesters.

Subedi said he was also concerned that some workers and trade union leaders have faced threats and intimidation as a result of their involvement in industrial action.

And he said the "violence and excessive force" used against protestors had "cast doubts" on any expectations that democracy in Cambodia was maturing and "marked a worrying change" in the government's response to public protests.

Separately, an end to violence in Cambodia's garment sector and the resumption of minimum wage negotiations was this week urged by six leading trade associations representing North America's apparel brands and retailers.