Hong Kong - A letter written by Jaycee Chan to his mother while in detention helped to lighten his sentence for a drug offence, said a report.

The three-page letter in which he apologised to his mother, former actress Lin Feng-jiao, moved prison staff who felt he had shown remorse over his offence.

That was one reason for the six months' jail sentence meted out to him last Friday in a Beijing court for providing a venue for drug users, said Apple Daily, which quoted from a story in Ming Pao Weekly.

Jaycee, who was arrested in Beijing with Taiwan actor Kai Ko on Aug 14 last year, will be released on Feb 14.

The sentence reportedly came as a relief to his parents as Jackie Chan, his movie star father, had heard that he would be locked up for two years.

Ming Pao Weekly cited unnamed sources for its report.

In his letter, the 32-year-old complained of his father's "insufficient love" for him, as he told his mother why he fell into the drug habit.

The actor said that, born into a celebrity family and as the son of the megastar, he shouldered enormous stress.

Although he led a carefree life coming from a rich background, he felt he faced a blank future.

He said that after he mistakenly met the wrong friends and was introduced to drugs, he would use drugs to forget his problems.

He said he regretted his error, promised not to be wilful and to turn over a new leaf.

Lin received the letter, which was seen by prison staff for security checks, 10 days ago, Ming Pao Weekly said.

The court was also lenient to him because of his voluntary confession and cooperation while the case was being investigated, it added.

Before the sentencing, his father had publicly stressed he had not used his connections to save his son, nor would he instruct his lawyer to help him get out soon.

Some 117.7 gms of marijuana were found in Jaycee's Beijing home. He admitted to providing a venue for drug users, including Ko, four times since 2012. Both tested positive for marijuana.

He grew up not being able to acknowledge Chan publicly as his dad as the movie star feared upsetting fans. Lin raised him in the United States while Chan was busy with his career.

Meanwhile, Ko, who had vowed to smoke less and quit pubbing after his arrest, was late on Saturday seen smoking and enjoying himself with friends at a Taipei bar, Apple Daily reported.

He later said through his agent that he was merely there to help a friend who wanted to open a restaurant to sample dishes. To him, Saturday's outing was not pubbing which involves people drinking and dancing.

As for his smoking, he said he is indeed trying to smoke less. He was detained in Beijing for two weeks before returning to Taiwan.