The Amnesty International said the human rights condition in the SAR last year has been the worst since the city's handover in 1997.
The advocacy group says Beijing's interpretation of the Basic Law to disqualify democratically-elected legislators had damaged the rule of law here.
It added that the disappearances of local booksellers about a year ago had caused people to worry about their freedom of expression.
The group's chairperson, Raees Baig, said the decline in press freedom is also another cause for concern.
“We see this [last] year there are escalating cases of violence against reporters, and there are very very confined space of press freedom or freedom of expression … is this the worst year? I guess we can generally say yes”, she said.
In the report, Amnesty said the disappearances of booksellers had raised alarm over whether the physical safety of Hong Kong people is sufficiently guaranteed.
Beijing’s interpretation raised questions about the autonomy of the city's judiciary, the report said.
Attacks on journalists by police officers without a criminal investigation and attempting to deter residents from exercising their rights to freedom of assembly were further challenges, it said.
"The government has a responsibility to ensure that citizens can express their views freely without fear," the report added, saying authorities should not invoke "obscure laws" to intimidate the public. (Additional reporting by AFP)