"Demonstrators continued to claim that their ability to protest had become increasingly difficult due to Hong Kong Police Commissioner Andy Tsang," the report said. "Some activists also alleged that police faced no penalty for making arrests that ultimately were not prosecuted or were dismissed by the courts."

Tsang said that of about 7,500 public events held last year, only 40 involved police arrests.

"Nearly 70 per cent [of the arrests] were made because other people's rights or property were affected," he said. "The police took action on reports. I totally disagree with any remarks that say the police suppress freedom of expression or assembly."

Earlier, police sent a serious crime unit from the Sha Tin district crime squad to investigate a case involving graffiti that said "Xi Jinping Go To Hell", which appeared on a wall at Kam Kwai House, Kam Fung Court, Ma On Shan. A man was charged with criminal damage and will appear in Sha Tin Court on Wednesday.

The report said the Basic Law "limits the right of residents to change their government peacefully. The government stated that the current method of selecting [functional constituency] legislators did not conform to principles of universal suffrage, but it took no steps to eliminate the FCs".

The report cited complaints over the handling of a June 7 report on the death of dissident Li Wangyang as an example of what some media watchers said was a troubling sign for press freedom.

Hong Kong Human Rights Monitor director Law Yuk-kai said the 2012 report levelled "straightforward and severe criticism" against the city's human rights condition.

A government spokesman said the advice of the Department of Justice would be sought if police intended to press charges against anyone arrested over public order.