An award-winning Hong Kong journalist was found guilty on Thursday of improperly searching a public database of vehicle licence plates to help track down the perpetrators of an attack on democracy supporters by government loyalists.

The conviction of Bao Choy, a producer with public broadcaster RTHK, comes at a time of deepening concerns over press freedom in the international business hub as Beijing stamps out dissent in the wake of huge democracy protests.

Choy, 37, was found guilty on two counts of "knowingly making a false statement" to access number plate ownership records.

"Members of the public do not have an absolute right to obtain any document under this ordinance," principal magistrate Ivy Chui said.

Choy faced up to six months in jail but was ultimately fined HK$6,000 ($770).

Colleagues and members of RTHK's employee union gathered outside the court holding banners that read "Journalism is not a crime" and "Who wants the public kept in the dark?"

"Though I was found guilty I still believe journalism is not a crime and searching registries is not a crime," Choy told reporters.

The database searches were made for an RTHK documentary last year called "Who Owns The Truth?" that investigated an attack on pro-democracy protesters by a gang of men armed with clubs and sticks.

The police's failure to respond quickly enough to the July 2019 assault was a turning point in the huge and often violent pro-democracy protests that year, further hammering public trust in the force.

RTHK used footage from witnesses and security cameras -- as well as number plate searches and interviews -- to piece together events.

It uncovered new details about the alleged attackers, some of whom have links to politically-influential rural committees that support Beijing.

It also said that police failed to respond to the build up of stick-wielding men ferried into the district by specific vehicles that evening hours before the attack.

Hong Kong maintains a publicly-accessible licence plate database long used by journalists, including pro-Beijing news outlets.

But authorities introduced a rule change that meant journalists were no longer allowed to make searches.

During her searches, Choy ticked a reason box that said "traffic and transportation related matters".

Bao Choy's case has deepened media freedom fears as Beijing has moved to stamp out dissent in Hong Kong
Bao Choy's case has deepened media freedom fears as Beijing has moved to stamp out dissent in Hong Kong AFP / Anthony WALLACE

But Judge Chui ruled media reporting was not covered.

Choy's lawyers argued her searches served the public interest and helped Hong Kongers "get closer to the truth".

"Today is a dark day for Hong Kong journalists," Chris Yeung, head of the Hong Kong Journalists Association, said on Thursday.

Authoritarian mainland China heavily censors the media.

But semi-autonomous Hong Kong remains an Asian press hub with a vibrant local scene and many international outlets hosting regional headquarters.

The city has slid down media freedom rankings in recent years however.

Reporters Without Borders (RSF) now ranks Hong Kong 80th in its annual global media freedom list, down from 18th in 2002.

Beijing has cracked down on opponents following 2019's protests, imposing a sweeping national security law and unveiling plans to ensure only "staunch patriots" run Hong Kong.

On Tuesday RSF warned China's "censorship virus" had spread to Hong Kong, adding that the security law was a "grave threat" to journalists.

The same day the city's police chief called for a "fake news law" to "assist national security".

Hong Kong's government dismissed RSF's report as "appalling".

Beijing has made no secret of its desire to see Hong Kong's critical media tamed and RTHK has increasingly found itself a government target.

Modelled on Britain's BBC, it is publicly funded and was editorially independent of Hong Kong's government.

But authorities have ordered an overhaul of the broadcaster, including the recent appointment of a career civil servant as its new head.

He has vowed to vet all programming and has pulled multiple shows, sometimes just days or hours before they were due to air.

RTHK suspended Choy after her November arrest and did not make any statement in support of her work.

On Thursday Gladys Chiu, from RTHK's union, said the broadcaster did not contribute to Choy's defence.

RTHK declined to comment on Thursday.