Ambiga Sreenevasan, president of the Malaysian Bar Council, says such allegations cannot be ignored.
In a country with a population of 27 million, she says, Rela has a membership of about 500,000.
"That's a frightening prospect because what they're doing is they're going into premises, there are cases where they have broken in, they've used gangster tactics and we are very concerned with the human rights abuses."
On the mission Al Jazeera followed, Rela commanders were keen to demonstrate that everything was above board.
|Rela has around 500,000 |
volunteers across Malaysia
But since Rela's powers were expanded almost two years ago there have been a chorus of complaints and allegations of abuse.
Za Uk Ling, a Burmese national working legally in Malaysia, recently fell victim to a Rela squad.
"Right before they got me into the van, I resisted and they were about to beat me," he says.
"I was lucky enough that one immigration officer was present and she told them not to use violence because there were a lot of people watching."
The Malaysian government and Rela bosses are quick to admit that there have been some problems but, they insist, only from a few rogue elements.
"Maybe one or two did that, I am not denying that," says Zaidon Bin Haji Asmuni, Rela's director-general.
"But that's a very small percentage compared to what Rela has actually done."
And the government says what is more important is that Rela is proving effective in countering what they call Malaysia's second most important security challenge - illegal immigration.
Most Rela volunteers, too, believe that illegal foreigners are to blame for what they say is a rising national crime rate.
|Human rights groups have condemned |
alleged abuses by Rela members
They believe these illegal workers are taking jobs away from deserving Malaysians and must be arrested.
With a small force of about 1,600 personnel, Malaysia's immigration department says it is dependent on Rela's help.
"Since the start of the year, Rela has arrested 15,000 illegal migrants," says Ishak bin Mohamed, Malaysia's immigration enforcement director.
"If we only had the immigration police force to rely on, we would not even be able to arrest 10,000 illegal aliens in a year. So Rela has been a major help to the immigration department."
On the raid Al Jazeera followed more than 100 men were arrested.
Those that fail to produce proper legal documentation face possible whipping and will be deported.
The government pays Rela the equivalent of about $25 for every illegal immigrant it finds.
|The government says Rela is vital |
to controlling illegal immigration
Irene Fernandez of Tenaganita, a migrant workers' rights group, says such incentives only encourage Rela members to "go all out" and arrest as many suspected illegal workers as possible, despite the fact that volunteers have little or no training.
"It's a very racist kind of perception that all migrant workers are a threat to Malaysia," she says.
With growing allegations of abuse, human rights groups say Rela has become a vigilante force and are calling for the government to review the group's operations.
Rather than relying on a volunteer force to round up suspected illegals, they say what is needed is stronger action against employers who knowingly hire them.