Asked to elaborate later, he said: “There were a lot of cases in the last two or three years. From the storming of the PLA barracks, to the Occupy protests, the Mong Kok riots, there were a series of such cases.”

While the judiciary declined to comment, the Justice Department said it would “control criminal prosecutions, free from any interference” in accordance with the Basic Law.

The department had to consider all relevant laws before proceeding with prosecution. And while the end outcome might not be consistent with “so-called general public expectation” – which in itself could be diverse and “universal” – it had always handled all criminal cases in a fair, impartial and professional manner, it said.

Watch: Hong Kong protest after Beijing ruling

Chen also chided the city’s legal profession for opposing the interpretation either because it “lacked or had a different understanding or it was using the law as a tool for political struggle”.

Legal sector lawmaker Dennis Kwok said he welcomed dialogue with Chen if he did not understand the sector’s traditions.

Speaking at the same seminar, Wang Zhenmin, legal department head of Beijing’s liaison office and a former law dean of Tsinghua University, said 15 lawmakers had “messed up” their oaths. He did not name them.

Among the 14 identified by the Post, all said they had taken their oaths solemnly and sincerely, and questioned Chen’s authority to cite categories of misconduct.

Chen, now president of the semi-official Chinese Association of Hong Kong and Macau Studies think tank, also said there were “a lot of people” who did not meet the legal requirements.

Watch: Hong Kong’s leader supports Basic Law ruling

Chen said: “With the central government’s interpretation, there are clear legal provisions to follow in tackling these acts that were insincere and not solemn.”

“All Chinese, all Hong Kong residents are watching, and will offer their strong support to Hong Kong’s executive, legislative and judicial branches as they exercise justice with the ‘sharp weapon’ provided by Beijing to restore Legco to normality and order,” he said.

Asked if he believed up to 15 lawmakers should be disqualified, Chen said the city’s authorities were better placed to decide. The fight against independence advocacy was “warfare that will be won”, he said.

In September, the pan-democrat and localist camps won 30 seats in Legco, while the pro-establishment camp grabbed 40.

Chinese University political scientist Ivan Choy Chi-keung warned it would be “unwise” for the authorities to expel half of the democrats.

“Mainstream public opinion has shown disfavour towards Leung and Yau already ... If Beijing is seeking to disqualify 15 lawmakers, it means they are not just fighting independence advocates, but launching a full-scale purge of dissident voices,” Choy said.

Additional reporting by Joyce Ng, Jeffie Lam and Emily Tsang