The plaintiff, Wong, would not comment on the case, citing the ongoing legal proceedings as a reason.

But he said he voted on Sunday. “After that, I was very happy … that Wong Kwok-hing helped me to mount this legal proceeding,” Wong said in Cantonese with a Mandarin accent.

Asked who was funding the case, Wong, described as a civic-minded citizen in the court document, said: “I will take care of it all.”

He did not respond to inquiries on whether he had an estimate in mind or would seek legal aid, as Wong Kwok-hing dismissed these as “hypothetical questions”.

Au said the judicial review was outrageous. “The people voted, we should respect the results,” he said, adding that Wong was being a sore loser. The newly elected lawmaker said he respected the Basic Law, even if he opposed an interpretation of the mini-constitution by Beijing.

He is also seeking a temporary ban on Au taking office, as well as for the decision to be gazetted.

The court papers said the nomination form Au signed stated that he would uphold the Basic Law and pledge allegiance to Hong Kong, a requirement listed in the ordinance.

Will pro-democracy camp learn the right lessons from shocking setback?

The incident also came up in a televised debate last month when Au’s main rival Judy Chan Ka-pui, of the pro-establishment New People’s Party, challenged him about it. At the time, Au said he had only burned a prop.

“Accordingly, [Au] never intended to and will not uphold the Basic Law and pledge allegiance to the Hong Kong Special Administrative Region,” the document said.

The paper cited another debate arranged by RTHK on March 7, in which it quoted Au as saying he would not mind doing it again in future protests if necessary.

Wong accused Au of not giving meaning to the words when he signed the declaration in the nomination, thereby rendering it “false” and “not genuinely or truthfully made” when it came to complying with the Basic Law. He added that as Au said he would do it again showed he did not have the will to uphold the oath as required by the law as well.

Turning to the returning officer, the court document said Teng had no power to declare Au’s candidacy valid because Au had not complied with the statutory and constitutional requirements.

Wong Kwok-hing said throughout March, some Hong Kong Island residents had made multiple complaints to the returning officer, as well as Barnabas Fung Wah, chairman of the Electoral Affairs Commission, but to no avail. Wong, the plaintiff, therefore decided to take the matter to court.

Ask why the legal action was not filed as an election petition instead, Wong Kwok-hing said: “It is not an election question but one of candidacy.”

Meanwhile, former civil servant Kwok Cheuk-kin is expected to lodge a judicial review application against newly elected pro-establishment lawmaker Vincent Cheng Wing-shun. Cheng belongs to the Democratic Alliance for the Betterment and Progress of Hong Kong.

Kwok – dubbed Hong Kong’s “king of judicial reviews” – said the full Chinese name of the political party could be partly translated as “democracy to build Hong Kong”. He argued that it would amount to promoting independence.

Additional reporting by Sum Lok-kei