"But if the intention is to them lock up, it will not be acceptable."
Efforts by police to regulate foreign labourers' movements would violate their basic rights, he said.
Malaysia, with a population of about 27 m, has long attracted migrant workers from poorer neighbours such as Indonesia, Myanmar, India and Bangladesh.
Many of them work in menial plantation or construction jobs that most Malaysians refuse to do.
The government has said about 1.8 m foreigners work legally in Malaysia, while an estimated 700,000 others lack proper documents.
But the government has come under pressure recently amid reports of a growing crime wave and other social problems that some blame on foreign – particularly Indonesian - workers.
Malaysia has staged periodic crackdowns
on illegal foreign workers[EPA]
According to police of the 230,000 crimes reported in 2006, some 5,000 were committed by foreigners.
Last week Radzi Sheikh Ahamad, the Malaysian home minister, said his ministry intended to propose a bill calling for the confinement of about 2.5 m foreign workers.
The chief of police Malaysian police Chief Musa Hassan said the proposal was meant to curb crime by monitoring foreign workers' activities and restricting their movements.
Under the plan workers would not be allowed to leave their living quarters unless they registered with their employers, who would be responsible for their movements.
Malaysian and international rights groups have condemned the idea, saying it could appear to be racial profiling and worsen already poor living conditions for foreign workers.