The US and its allies should jointly respond to China’s live ammunition drills designed to intimidate Taiwan by holding “freedom of navigation” operations in the Taiwan Strait, Taipei’s official representative to the UK has said.

In an interview with the Guardian, Kelly Wu-Chiao Hsieh also called on the UK to uphold the principles of rules-based international order and forge closer trade and security investment relations with Taiwan. He welcomed the decision of the foreign secretary, Liz Truss, to condemn the unprecedented Chinese military exercises in the wake of the visit of the US House speaker, Nancy Pelosi, to the island, the most senior US official to visit Taiwan in 25 years.

The UK, like most western countries, does not recognise Taiwan and has no formal defence ties with the country.

Hsieh said the events in Hong Kong had changed the views of many in Taiwan about China. “There is a new generation of young Taiwanese voters who have been hugely affected by China’s treatment of Hong Kong and have come to realise the Chinese promise of ‘one country, two systems’ was simply a facade or a joke. Many of these young voters are politically active, and are determined not to suffer the same fate as Hong Kong’s civil society movements.

“For decades China has promised it will not interfere with Taiwan after unification, but since 2020 that is not credible.”

He said: “The scale of these drills were different to what has happened before, and could not have been prepared, and all those resources lined up, in a very short period of time. It was premeditated, preplanned. It was only a matter of choosing the timing, and they just chose Pelosi’s visit. It was a self-orchestrated crisis.”

But he insisted the Chinese response would not intimidate Taiwan or stop its supporters from visiting the country. A UK foreign affairs select committee delegation is due to visit the capital, Taipei, before the end of the year.

Hsieh said the Chinese had used the Pelosi visit as “a pretext to mount its military exercises” and that, although the drills did not themselves amount to a blockade, “it does not take much imagination to work out what the Chinese are thinking about. They are trying to create a new status quo”.

A response asserting the principle of freedom of navigation – international laws protecting freedom of movement at sea – was needed in the next few weeks, Hsieh said, to protect the “median line” in the Taiwan Strait, a tacit maritime boundary between China and Taiwan that has existed since the 1950s. During the week of exercises China passed the median line, defined by Hsieh as the defining indicator of peace and stability in the Strait, by sea or air more than 100 times.

Millions of cyber-attacks also hit the self-governed island, including the president’s office, the foreign ministry and the defence ministry, Hsieh said.

“Even though China has announced the end of the formal drills, the reality for us is we experience these military drills still humming around us on a daily basis. So anytime in the future, maybe in the next few days, they might just resume again. The key [thing] to watch is if they continue to mess around with the median line,” he said.

Asked if an invasion is now inevitable, he said: “Inevitable or not, we we have to make sure that it is credibly deterred. Taiwan will fortify its defence capabilities and continue to look for international solidarity.”

He acknowledged that China has the ability to intimidate other countries in the region diplomatically, and said that until the G7 statement on the drills there had been “an eerie quietness”. The US National Security Council coordinator for Indo-Pacific affairs, Kurt Campbell, has since summoned the Chinese ambassador to the US to deliver a warning over the military exercises, while Truss conveyed a similar message to the UK’s Chinese ambassador on Wednesday.

Truss has landed herself in diplomatic hot water by urging the British government to do more to help Taiwan defend itself militarily. Neither the US or the UK have explicitly said how they would respond if China invaded Taiwan, but UK licences for arms exports to Taiwan have grown in the past two years.

Hsieh also confirmed Taiwan and the UK were discussing ways to boost bilateral trade agreements focusing on solar energy, biosciences, hydrogen power, transport infrastructure and the resilience of the supply chain for semiconductors (computer chips), an industry Taiwan dominates. “We are currently in the middle of clarifying areas for the future,” he disclosed.

China has condemned the trade contacts.