“I am very worried that the authorities would reject using my testimony and reject me attending court to testify against those attackers,” Lam said. “In the end, would the attackers be released through the lack of evidence?”

He added that officers had arranged to take further testimony last month, after he held a press conference saying he had more video clips and information about the attack.

But Lam said an officer called and cancelled the appointment on July 29, the day he expected to give another statement. The policeman said his colleague had to undergo a Covid-19 test.

On August 6, Lam’s office received a letter from police, thanking him for “fulfilling a citizen’s responsibility in reporting this serious crime to the police”, and they had not rescheduled a time to see him since then. The cases against the white-clad suspects are set to start in the District Court in February next year.

“I believe since the end of last month, my role as a key witness has been changed to a defendant,” Lam said.

Challenging previous media reports of the incident, Senior Superintendent Chan Tin-chu of the New Territories North regional headquarters said a police investigation concluded both sides were “on equal footing” in their use of force.

Calvin So, a chef believed to have been the first person attacked, said he was hit by a group of 20 men outside a shopping centre connected to the railway station, and questioned the police version of events.

“I was beaten by a big group of people, how equal footing can it be?” he said. “The group of white-shirted men gathered around as early as 6pm or 7pm, and I was beaten before 10pm. My case has proved [the police’s] script to be not sensible.”

Lam said his arrest had bolstered his determination to serve in the Legislative Council’s extended term after elections were postponed due to the coronavirus pandemic.

The opposition camp has been divided over whether lawmakers should stay, with some arguing they must hold the administration accountable, while others are pushing for a boycott.

“If we all withdraw from Legco, I believe our voice would be weakened and even silenced,” Lam said.

As a lawmaker, he received international media attention and had used his position to question officials and the government, he said, adding: “We have to keep this shed of light, no matter how weak it becomes.”

The Democratic Party plans to carry out a survey to gauge the public’s view on whether lawmakers should continue to serve in Legco, and the results will be respected, Lam vowed.

Labour Party lawmaker Fernando Cheung Chiu-hung earlier said the arrest of Lam and others had forced him to reconsider staying on as a legislator. The government was ready to “rewrite anything and completely subdue themselves under the command of mainland officials”, Cheung said.

During a special Legco House Committee meeting on the latest pandemic response measures, a group of opposition lawmakers held up placards and chanted slogans accusing authorities of “turning black into white”. All but two pan-democrats – who support boycotting the extended term – attended the meeting, alongside Chief Secretary Matthew Cheung Kin-chung and nine ministers.

When asked by reporters about the recent arrests, he said it would be up to the courts to handle as any prosecution must be based on evidence.