Boris Johnson has been challenged by his predecessor Theresa May as to whether the newly signed Aukus defence pact between the UK, US and Australia could lead to Britain being dragged into a war with China over Taiwan.
The intervention came during a Commons debate on the three-country agreement, under which the US and UK will share sensitive technology with Australia to allow it to develop its first nuclear-powered submarines.
The former British prime minister asked Johnson: “What are the implications of this pact for the stance that would be taken by the United Kingdom in its response should China attempt to invade Taiwan?”
In reply, the prime minister was careful not to rule anything out. “The United Kingdom remains determined to defend international law and that is the strong advice we would give to our friends across the world, and the strong advice that we would give to the government in Beijing,” he said.
Beijing has been adopting an increasingly aggressive stance towards Taipei, which has long received military support from the US. Military demonstrations are frequent: this month China sent 19 aircraft, including several nuclear-capable bombers, into Taiwan’s “air defence identification zone”, on the eve of Taipei’s annual war games exercises.
The three western partners have tried to downplay the impact of the Aukus agreement on China, although nuclear-powered submarines will allow the Australian navy to match Beijing, with vessels able to submerge for months at a time.
China reacted critically overnight, with the foreign ministry spokesperson, Zhao Lijian, saying it questioned Australia’s “commitment to nuclear non-proliferation” and accused the three countries of adopting an “obsolete cold war zero sum mentality”.
Johnson also told British MPs the Aukus agreement was not aimed at the east Asian superpower, in response to a question from the opposition leader, Sir Keir Starmer.
The prime minister said: “He began by asking whether it was in any sense adversarial to China and how we would manage the relationship with China, and I think it is important for the house to understand that Aukus is not intended to be adversarial towards any other power.”
Starmer had asked: “What plan does the prime minister have to ensure that this new arrangement increases rather than decreases our ability to influence China?”
Other senior MPs called for a more openly assertive stance. Tobias Ellwood, the Conservative chair of the defence select committee, said: “We must work with but stand up to China. This is about a more coordinated, long-term strategy and challenging China’s increasing hostile dominance in the South China Sea.”
Australia will become only the seventh nation to possess nuclear-powered submarines – once the vessels are built in the next decade or so – and the first country to do so that does not have its own nuclear power, processing or weapons programme.
The Aukus partners intend to spend the next 18 months working out how to supply Australia with the nuclear reactors required to power a submarine, which is expected to involve a combination of US and UK technology. But it is unclear where the reactors will be built and where they will be decommissioned.