On December 12, the Department of Justice (DOJ) concluded there was not enough evidence to prosecute Leung.

Cheng’s critics, including lawmakers and legal groups, asked if Cheng had broken with usual practice by not seeking external legal opinion, given that a sensitive figure was involved.

Speaking soon after landing at Hong Kong International Airport on Friday night, Lam defended Cheng’s decision.

“From what I see, secretary Cheng does not have any conflict of interest in the incident; she does not have any relationship with Mr Leung Chun-ying,” Lam said.

“I also cannot see any bias that could have affected her decision, so the decision made by the Secretary for Justice was not one that might be misunderstood.”

Asked if the DOJ’s policy on seeking outside legal advice had changed, Lam said it was not possible for her to answer the question for the department and for Cheng.

Lam went on to say that she hoped the UGL saga, which had been a point of contention for four years, could finally end.

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“As a professional judgment has been made – that there was not enough evidence to press charges – I very much hope this incident can come to an end,” Lam said.

She also hit out at Cheng’s critics for pressuring the minister without good evidence, adding that Cheng will give further explanations if it is deemed necessary.

“This is not something the chief executive can instruct her to do,” Lam said.

Earlier on Friday, Chief Secretary Matthew Cheung Kin-chung told reporters three times that people should not dwell on the UGL case.

“I really want the community to respect the professional judgment of the Department of Justice (DOJ) on this particular case,” Cheung said.

“I’ve said before, people should not dwell on this matter.”

A DOJ spokeswoman said on Friday evening that the department was still following up on the invitation to attend a Legco panel meeting on January 28 to take questions from lawmakers.

“When an arrangement has been confirmed, we will send a reply to Legco,” she said.

Upon returning to the city from holiday on Wednesday, Cheng had said that outside legal opinion was only required in cases involving a member of the justice department.

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In two documents submitted to Legco in December 2017 and February this year, however, the department set out six situations, whereby external legal advice was sorted.

The documents stated that the department may seek outside advice “so as to address possible perception of bias or issues of conflict of interests”.

Commenting on Lam’s remark on his personal capacity, Bar Association chairman Philip Dykes said Lam’s remark seemed to contradicted with Cheng’s.

“[What Lam suggested was] there’s a possibility, an option, and they chose not to do it. But two days ago, the Secretary for Justice has said that choice would not arise because the only circumstances briefed out would be when justice department personnel was involved.”

Dykes stressed the perceived conflict by the public did not arise from the personal relationship between Cheng and Leung, but the perception that Leung was a former chief executive and senior appointee of a top consultative body in mainland China.

Grenville Cross, a former director of public prosecutions said he was surprised by Cheng being “wholly unaware of her own department’s publicly announced policy”, which was followed by all of her predecessors.

“As Cheng is new to prosecutorial responsibilities, it is alarming that her prosecutors have not clearly explained to her prosecution practise in politically sensitive cases,” Cross said.

Former deputy director of public prosecutions John Reading SC told the Post that the justice department always have the convention to seek an independent legal advice, as it protects the justice minister and top prosecutor from speculation.

“[The case of ] Donald Tsang was briefed out for advice, [the case of] Rafael Hui was briefed out for advice, that was the usual convention, certainly the time I used to work there [in the DOJ],” Reading said.

“I can’t think of any cases that are controversial – and I talked about that from the aspect of a senior government official, a chief executive or a former chief executive – that has not been briefed out.”

Despite Lam and Cheng’s appeals, pressure on the justice minister continued to be applied from both sides of the political divide on Friday.

New People’s Party chairwoman Regina Ip Lau Suk-yee said Cheng had made incorrect statements about the DOJ’s policy on seeking external advice.

“The explanation was not very satisfactory,” Ip said.

Ip, a former Secretary for Security, also said Cheng was the “least visible and accountable” justice minister to lawmakers, seldom attending Legco meetings.

Ip also said however the DOJ’s prosecutorial decisions should not be queried.

“We should not over-politicise the decision,” Ip said.

Civic Party leader Alvin Yeung said officials and the pro-establishment camp were trying to play down the apparent change in policy on seeking external advice.

“The Secretary for Justice has the sole responsibility to give an explanation on this change,” Yeung said.

Additional reporting by Kimmy Chung