They also have the right to bear and use firearms with legal immunity from prosecution, Human Rights Watch said.
"The government has set up what's little more than a vigilante force to target foreigners"
Brad Adams, Human Rights Watch
"The government has set up what's little more than a vigilante force to target foreigners," Brad Adams, Asia director at Human Rights Watch, said in a statement.
"Given RELA's repeated abuses, it should be disbanded right away."
Adams said the government "fans xenophobia through its use of RELA", referring to a recent raid on a factory where two Nepalese workers were injured.
RELA members have also reportedly detained refugees, asylum seekers and even foreign workers legally entitled to be in Malaysia, deliberately destroying their identification cards to legitimise their actions, the New York-based group said.
Commenting on the Human Rights Watch report a RELA spokesman said victims of alleged violence by the members should immediately lodge a police report instead of making unsubstantiated claims.
"The public should stop accusing our members and start providing strong evidence of the alleged violations"
"We always encourage victims to lodge a police report so that we can assist the police in investigations," he told Al Jazeera on Wednesday.
"The public should stop accusing our members and start providing strong evidence of the alleged violations."
The spokesman, who requested anonymity, said RELA volunteers are regularly reminded to stick to standard operational procedures and those who fail to comply are hauled up for disciplinary action.
He declined to elaborate further.
Following a public outcry over reported abuses, Malaysian authorities announced in April that leaders of RELA raiding teams must body search team members to make sure they do not steal or plant evidence.
Volunteers are also barred from carrying mobile phones on raids to prevent information leaking out to other groups.
According to HRW, despite these measures RELA members are continuing to carry out abuses.
On April 5, the group said, RELA members arrested about 20 Myanmar nationals including at least five who had been recognised as refugees by the office of the United Nations High Commissioner for Refugees.
It also pointed to another case in late March when a RELA team was charged with robbery after eight of its members stole belongings worth RM1,800 ($525) from a house they were raiding.
Also in March, the the HRW report said, an Indian immigrant was detained and held in custody for four days, even though he was in the country legally.
RELA was formed in 1972 to maintain public order but in recent years has primarily been used to round up undocumented migrants who fill a severe shortage of low-wage workers in Malaysia.