Lai read her oath slowly last week, pausing six seconds between every word. Wong had omitted “Hong Kong” in his rendition.

Watch: three Hong Kong lawmakers have oaths rejected

Explaining his decision, Andrew Leung said Lau’s approach “objectively showed she’s not serious about taking the oath and had no intention of being bound by it”.

He said Wong’s omission was “inadvertent” and allowed him to retake the pledge.

The Legco president also warned that a legislator who does not recite the oath properly could be ruled as having refused to take it.

“I would not say [Wednesday is definitely their last chance] but I sincerely hope they will follow the legal requirements in taking the oath seriously,” he said.

By law, Legco members are required to swear allegiance to the special administrative region of Hong Kong, and refusal to take the oath properly could lead to disqualification.

While Leung stated he would judge the legislators’ oaths “objectively”, he declined to lay out specifics for determining a valid one.

“I cannot say concretely [what’s not permitted] because there are many different variations [in what they may do],” he said.

“I will judge by two objective criteria. First, whether they have followed the oath in accordance with the law. And second, whether they took the oath in a manner that can show the person administering the oath that they understand the seriousness of taking the pledge.”

The Legco president added that the two Youngspiration legislators would need put their request to retake their oaths on Wednesday in writing. “Only then can I plan this in the agenda,” he said.

However, he accepted Nathan Law Kwun-chung’s oath despite a call from the pro-establishment camp to reject it.

Lau said she disagreed with the president’s ruling that she was “not serious”.

“Everyone could see I was very serious,” the lecturer turned lawmaker said. “The president should give me guidelines how many seconds I should pause [in between the words of the oath] in order to be considered ‘serious’.”

She added she would discuss with her team how to approach the oath at Wednesday’s meeting.

Following Leung’s ruling, Starry Lee Wai-king, chairwoman of the Democratic Alliance for the Betterment and Progress of Hong Kong, said her party still sought an apology from the two Youngspiration members.

Regna Ip Lau Suk-yee, head of the pro-establishment New People’s Party, said the president’s ruling was “clear and well-reasoned”. She added that while he lacked legal power to compel the lawmakers to apologise they had a “moral responsibility to do so”.

Leung is scheduled to administer the oath to the five on Wednesday.

Speaking ahead of the weekly Executive Council meeting, Leung said the government was highly concerned about the actions of Baggio Leung and Yau Wai-ching.

They also displayed a banner bearing the slogan “Hong Kong is not China” while being sworn in.

Their oaths were invalidated by Legco secretary general Kenneth Chen Wei-on.

“We will closely monitor developments today,” the chief executive said. “If necessary we will take follow-up action.”

The city’s top official, however, declined to elaborate on the follow-up plan.

On Monday, the Youngspiration pair indicated they might retake the oath properly in order to retain their seats in the legislature. But they remained defiant, stressing they would not apologise in the face of growing criticism and calls for their resignation.

Upon his return to Hong Kong from a trip to the Americas and the Netherlands, Financial Secretary John Tsang Chun-wah condemned the two localist legislators’ actions.

“Behaving improperly in the council chamber, or even saying things to insult one’s own nation, is very immature and ignorant,” he said. “These actions are disrespectful towards voters, Hong Kong society, the legislature and even themselves,” Tsang said.

“I hope they will take seriously [criticisms against them] and apologise for their inappropriate speech.”

The financial chief’s comments came as criticism against the Youngspiration pair mounted, with numerous adverts slamming them still appearing in various local newspapers.

One statement came from British Chinese groups and individuals.

“We need to enhance supervision in different areas,” he said. “Relevant government departments are highly concerned about the quality of service at these homes.”