British foreign minister James Cleverly urged China to be more open about what he called the biggest military build-up in peacetime history and said secrecy around its plans could lead to a "tragic miscalculation".
Relations between Britain and China are the worst in decades after London restricted Chinese investment over national security concerns and expressed concern at Beijing's increasing military and economic assertiveness.
In a speech at Mansion House in London's historic financial district on Tuesday, Cleverly said Britain should engage "robustly and constructively" with China despite what he called "revulsion" over the treatment of Uyghurs in Xinjiang.
In a warning over the future of Taiwan, Cleverly said invading the self-ruled island would destroy world trade, and distance would offer no protection from the "catastrophic blow" to the global and Chinese economy.
A spokesperson for the Chinese foreign ministry said on Wednesday that the greatest threat to peace in the Taiwan Strait was the "separatist acts of Taiwan independence and the connivance and support of foreign forces".
Cleverly's speech is the clearest attempt to explain Britain's approach to China under Prime Minister Rishi Sunak, who said at the end of last year that the so-called "golden era" of relations under former Prime Minister David Cameron was over.
In contrast to French President Emmanuel Macron's attempts to distance Europe from any involvement in a conflict over Taiwan, Cleverly said "no country could shield itself from the repercussions of a war in Taiwan".
Cleverly said Britain is open about deepening cooperation with allies in the Indo-Pacific and called for China to be clear about its military intentions.
"I urge China to be equally open about the doctrine and intent behind its military expansion, because transparency is surely in everyone's interests and secrecy can only increase the risk of tragic miscalculation," he said.
China claims Taiwan as its own and has not renounced the use of force to ensure eventual unification. It has also said it will defend its territorial sovereignty, maritime rights and interests.
"If the UK wants to maintain peace and stability in the Taiwan Strait, it should strictly abide by the one China principle and firmly oppose Taiwan independence and separatism," Chinese Foreign Ministry spokesperson Mao Ning said at a regular press briefing on Wednesday.
China demands that countries with which it maintains diplomatic ties to recognise China's position that there is only "one China" and that Taiwan is a part of it.
NO 'NEW COLD WAR'
While the leaders of France, Germany and Spain have visited China in the last six months and called for engagement with the world's second-biggest economy, the U.S. and Britain are taking a tougher approach to what they consider a growing threat from Beijing to their interests and values.
Britain has sought to limit national security threats posed by China while engaging in areas such as trade.
The foreign minister's annual speech to Mansion House normally sets out a range of foreign policy issues. But Cleverly's speech, apart from a few brief remarks on the evacuation of Sudan and Ukraine, focused solely on China, in what the foreign ministry said was recognition of its "huge significance" to global affairs.
Cleverly, who hopes to visit China this year, said it would be a mistake to isolate China and engagement is needed in areas such as climate change, pandemic prevention, economic stability and nuclear proliferation.
"It would be clear and easy – perhaps even satisfying – for me to declare a new Cold War," he said. "Clear, easy, satisfying – and wrong."
However, Cleverly said that Britain will protect its national security interests and call out Beijing if it breaks its international obligations or abuses human rights.
He used his speech to condemn the treatment of the Uyghur people in China's Xinjiang region.
Cleverly said China was building "a 21st-century version of the gulag archipelago" and "locking up over a million people at the height of this campaign, often for doing nothing more than observing their religion".
China has vigorously denied allegations of abuse in Xinjiang.
(Reporting by Andrew MacAskill, additional reporting by Liz Lee in Beijing; editing by Barbara Lewis, Nick Macfie and Josie Kao)