A man who pulled out of a suicide pact with his parents has been jailed for five and a half years after pleading guilty to helping the pair kill themselves.

The High Court heard that the parents of gambling addict Lau Ka-wai, 43, had sold their Yuen Long flat and borrowed money from other people to help him pay off debts totalling HK$1.8 million

Both parents suffered from chronic health problems and the prosecution told the court that Lau's mother, 66, had suggested all three should end their lives together.

On an evening in February last year, the family had dinner on The Peak before going home. Lau then helped his parents up to the rooftop of the building they lived in and the mother jumped to her death.

Before following suit, Lau's father, 73, asked his son not to kill himself after all, the court heard.

In sentencing on Tuesday, Justice Johnny Chan said the defendant had left his parents in despair.

Lau did not do anything to stop them from committing suicide and it was shocking and chilling that he didn't express sadness at their deaths in his mitigation letter, the judge said.

Chan said he had taken into account, however, Lau’s guilty plea and his clear criminal record.

In mitigation, the defence lawyer had said that Lau blamed himself for his parents' deaths and would visit their graves once he gets out of prison.