A pastor's son and pro-democracy campaigner has urged Hong Kong churches to do their part in standing up for freedom in the territory.

Samuel Chu, whose father Rev Chu Yiu-ming co-founded the Umbrella Movement, said Hong Kong churches had "fallen behind" in the struggle for democracy.

Speaking at a webinar organised by Union Chapel Church, Chu said Hong Kong churches had been "shying away" from taking a stand, and shown an "unwillingness to put their faith to the test politically".

With the exception of a few figureheads like his own father and Cardinal Joseph Zen, Chu said the Church had been relatively "inactive" in the struggle for democracy over the last few years, resulting in churches now "being coopted by the state".

Chu now lives in Washington DC, where he runs the Hong Kong Democracy Council. Despite now being a naturalised American, he was charged last month by the Hong Kong authorities with "inciting secession" and "colluding with foreign powers", which are crimes under the new National Security Law.

During Monday night's seminar, Chu said it was important for churches to play their part because the crackdown will not only affect Hong Kong.

"The rest of China is on the line here," he warned, adding that as the democracy movement moves underground, "soft networks" like the church will become "more vital" in keeping the cause alive.

Chu said the participation of pastors in the last year's pro-democracy protests showed some shift in the church but he suggested they need to go much further "while we are still on the street fighting".

"Because there will not be a sustainable long-term protest movement on the street unless some of these institutions, like churches and schools, continue to become more democratic, to become much more subversive, to become much more politically courageous in professing faith, and not to abstain from the role that they must play," he said.

Benedict Rogers, Christian Solidarity Worldwide's East Asia Team Leader and the head of Hong Kong Watch, said he wanted to see democratic countries like the UK, US and Australia coordinate a "punitive response" with targeted sanctions against Beijing and Hong Kong officials who violate human rights.

He called Britain's offer of a pathway to citizenship for BNO passport-holders "very significant" but urged the UK Government to do more to help younger activists who do not qualify.

"They're the most vulnerable," Mr Rogers warned.

He closed by saying that Britain had a moral obligation to act in light of its historical ties to Hong Kong, but also a legal responsibility under the Sino-British Joint Declaration, which enshrined the 'one country, two systems' principle.

"Hong Kong is basically the new frontline in the fight for freedom," he said.

"This is not just a battle for the rights and freedoms of Hong Kongers. It's a battle for freedom against tyranny and repression, and if the Chinese regime is allowed to get away with what they've done to Hong Kong, then Taiwan will be next and we ourselves could well be next."