A store assistant, who went on bus rides on his days off and touched the breasts of young women during the journey, was jailed for eight months and three weeks on Thursday.

Steven Wong Tuck Sou, 43, pleaded guilty last month to one count of outraging the modesty of a 18-year-old polytechnic student. He committed the offence on Dec 21 last year on a bus travelling along Upper Bukit Timah Road. Another count of molesting a 20-year-old on June 3 last year was taken into consideration by the district judge in the sentencing.

Upon his arrest on Jan 29 this year, Wong admitted to police that he had been molesting women on buses once or twice every month since last year. He would sit directly behind them and put his hand between the seat and the window to touch the side of their breasts.

If the victim merely shifted away, he would remove his hand. If she turned around to look at him, he would pretend to be asleep. When confronted, he would get off at the next bus stop. He said he did this only on days he was not working to kill the boredom.

Defence counsel Krishnan Sivanandam said that the Institute of Mental Health found Wong to be suffering from adjustment disorder and depression, which had contributed to the commission of the offences.

The lawyer also said that his client had been made a bankrupt in 2009 and had to move in with his in-laws. His father-in-law would scold him frequently so Wong would try to stay out and return home late.

Asking the court to impose a stiff sentence, Deputy Public Prosecutor Norman Yew cited newspaper reports that showed that outrage-of-modesty cases on buses and trains had increased by 30 per cent - from 114 cases in 2011 to 153 last year.