Sir Keir Starmer raised the “deterioration” of jailed pro-democracy activist Jimmy Lai when he met Xi Jinping.
The Prime Minister held talks with the Chinese president at the G20 summit in Brazil, where he also stressed he wants “respectful” relations between the UK and Beijing.
Sir Keir, who is the first UK Prime Minister to meet Mr Xi since 2018, also suggested a full UK-China meeting in London or Beijing as part of his desire for “consistent and durable” ties between the two countries
In a sign that he was prepared to challenge China over human rights abuses, he raised the case of Mr Lai, the pro-democracy activist and British national imprisoned in Hong Kong.
Journalists were ushered out of the room at the start of the bilateral meeting around the time Sir Keir mentioned Mr Lai.
The Prime Minister said: “I’m very pleased that my Foreign Secretary and foreign minister Wang met recently to discuss respective concerns including on human rights and parliamentary sanctions, Taiwan, the South China Sea and our shared interest in Hong Kong. We are concerned by reports of Jimmy Lai’s deterioration.”
The PM stressed recently at Prime Minister’s Questions that securing the release of the pro-democracy activist and British citizen from a Hong Kong prison is a “priority” for the new Government.
Mr Lai, aged 76, was arrested in 2020 for fraud and involvement in protests and, following delays, is now facing trial for sedition and collusion with foreign forces.
The founder of the now-defunct newspaper Apple Daily has pleaded not guilty, but would face life in jail if convicted.
Human rights groups have criticised his arrest and the United Nations Working Group on Arbitrary Detention says Mr Lai is unlawfully and arbitrarily detained in Hong Kong and has called for his immediate release
His son Sebastien Lai stressed recently: "My father will be 77 soon, he has spent close to four years in solitary confinement in a maximum security prison for peacefully campaigning for democracy in Hong Kong.
"As you can expect his health has deteriorated by a lot.”
The UK-China relationship has worsened in recent years, with concerns over security and human rights as Mr Xi imposes an increasingly authoritarian regime in China and adopts a more assertive foreign policy.
The sanctioning of Westminster parliamentarians critical of Beijing has further soured ties with China and relations are a long way from the “golden era” controversially sought by the Conservatives under David Cameron and his Chancellor George Osborne.
At the meeting in Rio de Janeiro, Sir Keir told the Chinese leader: “We want our relations to be consistent, durable, respectful, as we have agreed, avoid surprises where possible.”
He added: “The UK will be a predictable, consistent, sovereign actor committed to the rule of law.”
Sir Keir also said he was keen for Chancellor Rachel Reeves to meet vice premier He Lifeng “to explore more investment projects and a more level playing field to help our businesses”.
