Malaysia intensified its crackdown on activists and human rights movements in 2015, human rights watchdog Amnesty International said in report.
The report cited the arrests of government critics and the passing of tougher preventive laws.
"The crackdown on freedom of expression and other civil and political rights intensified ... Police used unnecessary or excessive force when arresting opposition party leaders and activists," Amnesty International said in its report on the country.
Amnesty noted that Malaysia received international criticism for the handling of the humanitarian crisis when thousands of Rohingya refugees came to Malaysia's Kedah province as they fled persecution in Myanmar.
The report said a combination of laws were used against street demonstrators in 2015, including the Peaceful Assembly Act and various sections of the Penal Code.
The report also cited the amendment of the Sedition Act, saying the highly contentious Sedition indicates a further "erosion of freedom of expression".
It said the new Prevention of Terrorism Act, which was passed last year, gives expansive powers to the government in dealing with dissent.
The report particularly highlighted the imprisonment of popular opposition figure Anwar Ibrahim last year under charges of sodomy.
Earlier this month Human Rights Watch called upon the Malaysian government to release Anwar, who has been embroiled in what it says is a politically motivated gay sex case for the last 15 years.
"Malaysia's conviction of Anwar Ibrahim was politically motivated, and he's already suffered through a year in prison from this travesty of justice," Phil Robertson, deputy Asia director of Human Rights Watch, said.
Last month, Malaysia was ranked 68th in a global democracy index prepared by the Economist Intelligence Unit (EIU), behind Indonesia and the Philippines.