A Christian human rights activist says Hong Kong's new security legislation could negatively impact freedom of religion in the region. 

China's ceremonial legislature, the National People's Congress, endorsed the security law on Thursday.

The law will alter the territory's mini-constitution, or Basic Law, to require its government to enforce measures to be decided later by Chinese leaders.

The law will criminalise secession (breaking away from the country), subversion (undermining the government) and terrorism (using violence or intimidation against people). 

Ben Rogers, Christian co-founder and chair of Hong Kong Watch told Premier it could destroy Hong Kong's basic freedoms. 

"I think the implications most people believe are that it will become potentially criminal for people in Hong Kong to engage with foreign parliamentarians.

"I think the right to peaceful protests will probably disappear or at least be very restricted."

Rogers added that the implications of religious freedom could be dire. 

"Although it doesn't say so explicitly, I think it's highly likely that pastors and priests' sermons may be monitored more closely.

"And those religious leaders who preach, for example, on issues of human rights and justice, churches and other places of worship that have in any way supported demonstrators taking part in prayer vigils, those sort of things could be effected definitely."

No 10 said the Government is "deeply concerned" about the new law.

Prime Minister Boris Johnson's official spokesman told a Westminster briefing: "The steps taken by the Chinese government place the Joint Declaration under direct threat and do undermine Hong Kong's high degree of autonomy."

Foreign ministers from the UK, Australia, Canada and US have urged China to work with the government of Hong Kong to find a "mutually acceptable accommodation that will honour China's international obligations" under the Joint Declaration.

The signatories to the joint statement - Foreign Secretary Dominic Raab, Australian foreign minister Marise Payne, Canadian foreign minister Francois-Philippe Champagne and United States Secretary of State Mike Pompeo - stated their "deep concern" over Beijing's move.

They wrote: "The proposed law would undermine the One Country, Two Systems framework.

"It also raises the prospect of prosecution in Hong Kong for political crimes, and undermines existing commitments to protect the rights of Hong Kong people - including those set out in the International Covenant on Civil and Political Rights and the International Covenant on Economic, Social and Cultural Rights.

"We are also extremely concerned that this action will exacerbate the existing deep divisions in Hong Kong society; the law does nothing to build mutual understanding and foster reconciliation within Hong Kong."

Activists in Hong Kong have complained that the law will undermine civil liberties and might be used to suppress political activity.

Rogers told Premier: "It's not just political activists or religious leaders who may be affected. I think, the ordinary citizen who might want to post a political joke on their social media or might want to express a comment on social media or even just to their friends about the Chinese regime or the Hong Kong government, and in doing so they will be in danger."

Beijing blocked a UN Security Council meeting to discuss the legislation on Wednesday, with China's UN ambassador, Zhang Jun, tweeting that Hong Kong is "purely China's internal affairs".

Hong Kong ceased being a UK territory in 1997 under an agreement with Beijing dubbed "one country, two systems" in which it was allowed some autonomy.

Listen to Premier's interview with Ben Rogers on Thursday here: