Keir Starmer will become the first UK prime minister in six years to meet the Chinese president, Xi Jinping, promising to turn the page on UK-China relations by building “a pragmatic and serious relationship”. Starmer and the chancellor, Rachel Reeves, have been pursuing a thawing of relations with the world’s second-largest economy on pragmatic grounds, suggesting that the UK cannot achieve its growth ambitions without better terms with China. But the move to deepen ties is likely to be controversial among human rights groups and backbenchers, and with several high-profile Conservative MPs who have had sanctions imposed on them by China. Tom Tugendhat and Alicia Kearns, both prominent Tory critics of China, called on Starmer to use the meeting to raise with Xi the plight of UK nationals including Jimmy Lai, the pro-democracy media owner detained and tried in Hong Kong. Starmer will meet the Chinese president on Monday in Rio de Janeiro at the G20 summit, a meeting of world leaders that is likely to be marked by divisions over the climate crisis and Ukraine. No British prime minister has met Xi since Theresa May visited Beijing in 2018 in the midst of a trade push during Brexit negotiations, though Boris Johnson spoke to the Chinese president during the pandemic. Since then, relations have significantly cooled because of cyber threats, a human rights crackdown in Hong Kong and the sanctions against British MPs. Rishi Sunak attempted to renew relations at the G20 summit in 2022 where a bilateral was planned but cancelled due to Ukraine developments. But Conservative leaders have toyed with designating China a threat to British security – stronger language than the US had used. Those to have had Chinese sanctions imposed upon them include Tugendhat, the former security minister; Nusrat Ghani, the Commons deputy speaker; and Iain Duncan Smith, the former Conservative leader. Tugendhat said: “Jimmy Lai – a British citizen – is being put on a show trial in Hong Kong. Others are being threatened here in the UK. “It is essential that Starmer raises Mr Lai’s case and the threats we are witnessing against other British nationals who have spoken out who are now here in the UK. Starmer must clearly defend Britain against Beijing’s authoritarian regime.” Kearns, who is a shadow foreign minister, said: “The sham trial of British citizen Jimmy Lai recommences on Wednesday, yet it is glaringly absent from Starmer’s comments. British interests are achieved by being set out clearly, not as ‘by the ways’ cast to the sidelines of discussions. Starmer needs to call for Jimmy’s release now, and be unequivocal with Xi Jinping.” The foreign secretary, David Lammy, visited China last month in the first signal that the new Labour government saw a renewal of better ties as a priority. Reeves, who is understood to be taking a leading role in pursuing new economic opportunities with China, will head to Beijing in January. In remarks before his meeting with Xi, Starmer sought to head off gloomy predictions for the summit, at which there will be a number of world leaders who are facing election defeat. Additionally, Russia’s president, Vladimir Putin, has said he will not attend the summit, but his foreign minister, Sergei Lavrov, will be there. “It is in the UK’s best interests to engage on the global stage – whether that’s building strong and fruitful partnerships with our closest allies or being frank with those whose values differ from our own,” Starmer said. The prime minister expects to meet at least eight world leaders in one-to-one discussions in Rio. Speaking to reporters en route to the summit, Starmer underlined the need for a realistic approach, saying it was important that he met Xi and stressing the potential economic benefits – without mentioning the potential security risks to better relations. “We are both global players, global powers, both permanent members of the security council and of the G20. China’s economy is obviously the second biggest in the world,” he said. “It’s one of our biggest trading partners and therefore I will be having serious, pragmatic discussions with the president when I meet him.” Asked if the intention was to improve on the relations since the Conservative government, Starmer said: “I do think it’s important that we have serious engagement, which is what I will be pursuing in my bilateral at the G20.” No 10 said that any change in relations would be “rooted at all times in the UK’s national interests” but said there were “clear areas of mutual cooperation – including on international stability, climate and growth”. It said Starmer would be “firm on the need to have honest conversations on areas of disagreement, while competing and challenging where we have to.” Starmer has faced some criticism at home for the number of days he has spent abroad since taking office, and this trip amounts to another four days away from the UK. Starmer defended the trip – the first visit by a British prime minister to Brazil in 12 years – as a chance to catalyse relations with rising economic powers in Latin America, suggesting common ground with Brazil’s leftwing president, Luiz Inácio Lula da Silva, on green energy and protecting workers’ rights. Lula is said to be pressing for a strong message in the communique on fair taxation of the wealthiest, but the Argentinian president Javier Milei, a close ally of Trump who was the first world leader to visit the president-elect at his Florida residence, is reported to be mounting a number of obstacles to the final text. He also raised significant objections on climate targets at the UN climate summit in Baku. Starmer denied the futility of a G20 meeting with such extreme division between the leaders in attendance – not just on Ukraine, taxation and the economy but on climate and gender equality. There is expected to be only a limited reference to Ukraine and Gaza. “We’re meeting the biggest economies in the world in the next few days and my No 1 mission is to grow our economy and to get inward investment into our country,” Starmer said. “So I’m going to use that opportunity at the G20 to do exactly that.”