“Attempting to silence voices globally that speak up for freedom and democracy is unacceptable and will never succeed,” Ms Truss said.

Hong Kong Watch was accused of colluding with foreign forces which is criminalised under the national security law imposed by Beijing in mid-2020 in an effort to squash pro-democracy protests that had roiled the city.

A letter from Hong Kong authorities said the group was “engaging in activities seriously interfering in the affairs of the [Hong Kong special administrative region] and jeopardising national security of the People’s Republic of China”.

Such activities included “lobbying foreign countries to impose sanctions or blockade, and engag[ing] in other hostile activities…and seriously disrupting the formulation and implementation of laws or policies [by the Chinese government]”.

Organisations close under national security law

The warning from Hong Kong authorities also confirmed that the organisation’s website, blocked in the city since at least February, had been censored under the national security law.

The law technically applies globally, although it is unclear whether and how Hong Kong authorities will enforce it in practice.

Since the national security law came into effect in July 2020, a number of politicians, activists, lawyers, doctors, and other professionals have fled Hong Kong out of concern that they would be targeted.