Najib has rejected criticism that the changes give the government powers similar to the Internal Security Act, a decades-old law that has been repealed but once allowed the Home Ministry to detain suspects indefinitely without charge. That act had mainly been invoked against militant suspects in the past decade, but political opposition members have also been held for allegedly threatening national security.
"Malaysia is taking a huge step (backward) on rights by returning to administrative detention practices much like the draconian Internal Security Act," Phil Robertson, deputy Asia director at Human Rights Watch, said in a statement Thursday.
"By doing so, Prime Minister Najib is backing methods that do little to curtail crime but threaten everyone's liberty," Robertson said.
Lim Kit Siang, a top opposition member of Parliament who has previously been held for months on separate occasions under the Internal Security Act, said the approval of the amendments marked "a black day for Malaysia."
Najib earlier this week said the changes were crucial to tackle an increase in organized crime, insisting that crime "has frightened the public and if the government doesn't act, more people will become victims." Malaysians have been concerned in recent months over robberies and high-profile public shootings of targets including businessmen.