Britain on Tuesday voiced fears at China's passing of a new national security law for Hong Kong, and said it would look to see if it broke an agreement between the two countries.
Both Prime Minister Boris Johnson and Foreign Secretary Dominic Raab said they were "deeply concerned" after the legislation was approved by Beijing's rubber-stamp parliament.
"We will be looking at the law very carefully, and we will want to scrutinize it properly to understand whether it is in conflict with the Joint Declaration between the UK and China," Johnson told reporters.
"And we will be setting out our response in due course."
Britain handed over Hong Kong to China in 1997 with a guarantee that it would preserve certain freedoms, as well as judicial and legislative autonomy, for 50 years.
Beijing maintains that the so-called "One Country, Two Systems" deal is still being respected but critics believe the new law threatens civil liberties in the financial hub.
Britain has repeatedly said it is worried about the impact of the law, which comes after protests last year against a proposal to allow extraditions to mainland China.
London has offered to extend visa rights to millions of Hong Kongers if the national security law was pushed through.
Raab again urged China to "step back from the brink, respect the rights of the people of Hong Kong, and... live up to its international obligations through the joint declaration".
He told lawmakers Britain remained committed to fulfilling its promises on visas and "any other action we want to take with international partners".
Johnson was asked whether Beijing's move would have an impact on Britain's decision to allow Chinese telecoms giant Huawei to work on the country's 5G data network.
"I'm not going to get into Sinophobia because I'm not a Sinophobe," he said.
But he added that said there was a need to "strike (a) balance" between protecting critical national infrastructure from "hostile state vendors".
Critics of Huawei's involvement believe some of the company's equipment has vulnerabilities that could be potentially exploited by nefarious state actors and hackers.
