The wife of Hong Kong Chief Executive Leung Chun Ying has defended her eldest daughter over her latest scandal, which involved the older woman being slapped twice by the younger one on camera during a night out to celebrate Halloween.

According to reports from the South China Morning Post and Apple Daily, a number of videos posted online show Ms Leung Chai Yan, 24, who was decked out in ghoulish attire and make-up, striking her mother Regina Tong twice in the face early on Sunday morning.

The incident took place as Ms Leung was being bundled into a taxi in the busy Lan Kwai Fong district.

It was not clear what caused the public outburst, but it is understood that the visibly drunk Ms Leung was causing a commotion on the streets before her mother appeared.

Ms Tong was seen recoiling in shock and cradling her face before attempting to get into the taxi with Ms Leung, who slapped her again and kicked her, then left for home with a male friend.

Ms Leung said to the crowd, which included reporters who had gathered at the scene at around 3am on Sunday: "You know this mum is not my actual biological mum?"

But her friend quickly warned her not to say anything more.

Ms Tong also did not comment on this claim. But she urged the media yesterday to leave her daughter alone, saying she was drunk and wanted to protect her friends

from the crowd of reporters, and had not meant to offend anyone, reported the South China Morning Post.

"Chai Yan is a kindhearted girl... (She) is innocent," Ms Tong was quoted by the paper as saying, adding: "She needs rest."

Netizens have flocked to Ms Leung's Instagram account to criticise her for being unfilial.

Lifestyle portal Shanghaiist reported that her Facebook page has been flooded with messages, and some have even demanded to know who her biological mother is.

In March, Ms Leung made a public announcement that she was being held at home against her will by her mother, who she claimed also physically assaulted her.

She then said she was "leaving home forever and never coming back".

That incident prompted Mr Leung to hold a press conference, where he announced that his daughter had been dealing with "some health problems".

The Chief Executive's Office has yet to issue a statement to confirm or respond to the latest incident.