Workfair Singapore, a group of civil society volunteers concerned about worker rights, said on Wednesday that it is "deeply dismayed" that some of the workers remanded on charges of rioting in Little India have complained of police assault in a place where there were no cameras.

The group said in a statement posted on its website that the allegation is extremely grave and deserves the full investigative weight of the authorities.

According to customary international law, codified by the United Nations General Assembly Declaration against Torture (1975) and Convention against Torture (1984), statements obtained by coercion or under duress may not be used in evidence, the group said.

It called on the Minister of Law to appoint an independent investigator, apart from the Public Prosecutor who has been asked by the judge to investigate, with full access to all the investigated persons and all the police officers who have had contact with them so as to facilitate an impartial and independent investigation and forestall any subsequent concerns of bias.

The group also noted that 53 of those investigated will be deported without benefit of trial. "The arbitrary deportation of these 53 persons raises grave concerns about the Rule of Law," it wrote online.

It added that the Controller of Work Passes should not have arbitrary powers to revoke work passes without the right of appeal, or the Police Commissioner to determine culpability. Criminal charges should be tried in court which is the constitutionally appropriate forum for their adjudication.