Amnesty International has condemned deteriorating human rights conditions in Cambodia in its annual world report, with one representative saying last year’s questionable court cases against rights workers, activists and opposition members constituted a “downward spiral”.

According to the report, published on Tuesday, “the authorities’ misuse of the justice system increased”. It goes on to list the arrests and continued detention of several human rights defenders, including the “Adhoc 5” – who were arrested early last year and detained since – and other activists and politicians, and the July murder of political analyst Kem Ley.

“At least 16 activists and officials from the opposition remained in prison after unfair trials,” it reads. The report alleges that human rights defenders were “threatened and arrested for peacefully carrying out their work”.

On the subject of Ley’s murder, which is widely believed to be a political assassination, the report argues that “the authorities failed to conduct an independent and effective investigation” into the case, “or to inform the public adequately” of any such investigations.

Champa Patel, director of Amnesty International’s South East Asia and the Pacific Regional Office, said in an email that last year marked a “downward spiral” that seemed to continue in 2017.

“Proceedings in the cases of political activists have tended to involve little and often no incriminating evidence,” she said, and cited the example of Ouk Pich Samnang’s conviction on a 2014 charge of intentional violence in July 2016.

She said footage showed no violence on his part and none of the witnesses said he used violence.

“None of this seemed to have mattered in the verdict and in the subsequent appeal decision,” she said.

United Nations Office of the High Commissioner of Human Rights country director Wan-Hea Lee agreed with this assessment.

“One of the principal ways in which Cambodia has traditionally been able to demonstrate progress and its relative openness has been to point to its active civil society and media,” she said.

But this was more difficult now, she said, “after so many persons have been and continue to be convicted for merely expressing an opinion”.

Executive director of the Cambodian Center for Human Rights Chak Sopheap echoed these concerns, saying the human rights situation “clearly declined” in 2016.

“Now, only two months into the new year, it increasingly appears that the situation for human rights in 2017 risks being even more dire than the year before,” she said in an email.

Opposition lawmaker Mu Sochua from the Cambodia National Rescue Party said she was particularly concerned about freedom of expression. “It’s vital for democracy, and it’s a fundamental right,” she said.

The recent amendment of the Law on Political Parties to provide a mechanism to dissolve opposition parties, she said, was a “form of violation of human rights”.

Recent defamation cases also distorted freedom of expression, she said. “If the members of media, reporters, fear and have to practice self-censorship, then this has an impact on the quality of information that I get, and therefore impacts the quality of my freedom of expression,” she said.

Ministry of Justice spokesman Chin Malin dismissed the credibility of the report. “The report is issued with a political agenda,” he said. “It does not reflect the real situation.”

He condemned it as one-sided, saying it did not collect data from the government. “It does not reflect another angle, namely whether those [arrested] people have committed illegal acts or not,” he said.

Multiple other government representatives could not be reached yesterday.

Additional reporting by Mech Dara