Australia, Britain, Canada, New Zealand and the US accused China of orchestrating a concerted campaign to silence all critical voices in Hong Kong and breaching international obligations.
The Five countries, part of an intelligence alliance called Five Eyes, said they had "serious concern" over China's disqualification last week of four pro-democracy lawmakers in Hong Kong and demanded they be reinstated.
"Following the imposition of the National Security Law and the postponement of September's Legislative Council elections, this decision further undermines Hong Kong's high degree of autonomy and rights and freedoms," they said in a joint statement.
They added that China's action "is a clear breach of its international obligations" under the UK-China Joint Declaration signed between the two countries before the territory was handed back to Beijing in 1997 and that "the disqualification rules appear part of a concerted campaign to silence all critical voices".
"We urge Chinese central authorities to re-consider their actions against Hong Kong's elected legislature and immediate reinstate the Legislative Council members," they said.
Beijing imposed a national security law on Hong Kong late in June. The legislation, which makes "secession, " "subversion", "terrorism" and "collusion with foreign forces" illegal, has since been used to arrest pro-democracy protesters and lawmakers.
A month later, authorities barred 12 prominent pro-democracy figures from running in the parliamentary election scheduled for September before postponing the ballot by a year citing concerns over the COVID-19.
Only half of the Legislative Council's (LegCo) 70 seats are directly elected by voters. Another 30 are indirectly elected by interest groups while the remaining five seats are filled by district councillors elected by the public.
Another law, this time barring anyone deemed"unpatriotic" from holding office, was also passed and used last week to expel four pro-democracy lawmakers from the LegCo. The rest of the pro-democracy caucus resigned en masse in protest.
On Wednesday, three former pro-democracy lawmakers were also arrested for disrupting legislative meetings months ago.
The national security law was strongly condemned by rights groups and western nations as undermining the rule of law and restricting freedoms. Multiple countries including the US and UK have suspended their extradition treaties with Hong Kong with Washington also slapping sanctions on the city's Chief Executive, Carrie Lam, and 10 other high ranking officials.
The EU has also restricted exports of surveillance equipment to Hong Kong.
China refutes it is cracking down on dissent in Hong Kong.