“The US consul general in Hong Kong blatantly supported Jimmy Lai [Chee-ying] and other anti-China disrupters in Hong Kong, and interfered in Hong Kong affairs and [mainland China’s] internal affairs.”

The spokesman added the office expressed its “firm opposition and strong condemnation”.

“With or without a fake news law here, Hong Kong’s media is under increasing control and restrictions on what they can report,” he said. “That’s very evident when you’re here week to week, month to month.”

He added that businesses and individuals would appreciate “a stronger and clearer assurance” that the internet would remain free and open and the city would avoid the restrictive data control that “made life very difficult” for foreign companies across the border, as it was Hong Kong’s “biggest advantage” over the mainland.

May said the US was interested in stabilising its relationship with the city, but the government would need to stop “the slide towards ever greater repression”.

“I note that the backsliding here on rights and freedoms, it’s not just a concern of the United States alone, [but] many countries,” he said.

He also accused the city’s authorities of attempting to limit freedom of expression beyond its borders.

“This transnational repression through the use of bounties and intimidation of US citizens and US residents is unacceptable.”

May also claimed that authorities had been carrying out “soft repression” by increasing pressure outside the city’s legal system to diminish freedoms enjoyed by Hongkongers.

He said some legally registered groups had encountered difficulties in organising events as venues kept cancelling bookings at the last minute, while a political cartoonist was banned from publishing his work without any stated reason.

“I would argue that this self-censorship and authorities’ soft repression are arguably doing just as much to chip away at Hong Kong’s vibrancy, openness and rule of law,” he said.

The top envoy ended with a note of optimism that Hongkongers’ resilience provided hope for the future and they had been working hard to preserve what made the city special, such as its language and culture.

China’s foreign ministry arm in the city said the central government had always comprehensively, accurately and unswervingly implemented the principles of “one country, two systems” and “Hong Kong people governing Hong Kong”, while also ensuring a high degree of autonomy for the city.

“In the 27 years since its return to the motherland, Hong Kong’s practice of one country, two systems has been a success recognised by the world,” he said, referring to the principle governing ties between the city and Beijing.

Lawmaker Lai Tung-kwok, a former secretary for security, called May’s comments unfair. He noted the US had also taken steps to protect national security, citing the examples of its move to ban the social media app TikTok and imposing export controls on China.

“The US can do anything in the name of safeguarding national security,” he said. “The US has adopted different standards on national security issues of their own and the others.”

He said May did not provide any details on the allegations he made and had arbitrarily drawn conclusions.

The legislator stressed it was Hong Kong’s constitutional duty to enact its domestic national security law, while Beijing imposed its own version in 2020 following the violence of the 2019 anti-government protests.

The think tank held the online forum days after issuing its 40-page report titled “The Erosion of Hong Kong’s Autonomy since 2020: Implications for the United States”.

The report – backed by the US Department of State – was based on 35 interviews carried out by the authors in Hong Kong last September. The team spoke to former city officials, foreign officials, businesspeople, investors, academics and journalists.

It was crucial for the US to adopt the right strategy to protect what remained, the authors said.

The think tank said it doubted the effectiveness of taking a “penal” approach through sanctions against Beijing.

The authors added they also disagreed with a “resignation” strategy – the gradual removal of policy exemptions that treated Hong Kong differently from the mainland under US law – as it might also have the opposite effect from what was desired.

Major internet providers are now under pressure and conducting reviews on whether to remove the song from their online platforms.

Additional reporting by Edith Lin