A Senior Immigration Assistant has been sentenced to four years and five months in prison for misconduct in public office after he was found guilty of using the Immigration Department's chops to help Mainlanders stay in Hong Kong unlawfully, and of possessing other people's identity cards.

The District Court had earlier found Ngai Chi-keung, 38, guilty on five counts of misconduct in public office, and one of possessing other people's HKID cards.

In view of the offences' serious nature and the breach of trust involved, Deputy Judge Sham Siu-man said he had to impose an immediate custodial sentence on Ngai. He added Ngai's offences might have created confusion in the department's computer system on which the court and law-enforcement agencies relied. They also compromised the government's effort to combat the problem of illegal workers.

The Independent Commission Against Corruption investigated Ngai's case after the Immigration Department alleged that an officer might have accepted advantages from a syndicate for helping two-way permit holders extend their stay in Hong Kong unlawfully.

Ngai was working at the Hung Hom Station Control Point at the time he committed the offences, ICAC officers learned. Between December 2004 and April 2005, seven Mainlanders travelling to Hong Kong on two-way permits had approached Ngai with their travel documents themselves, or through a middleman, on several occasions.

He improperly applied his arrival and departure chops on the two-way permits of five of the Mainlanders while on duty at the Control Point. They indicated these Mainlanders had left and returned to Hong Kong when they had not. Ngai also made false entries in the department's computer system about their purported comings and goings.

Some of the Mainlanders had made payments of $50 to $1,500 to the middleman, who arranged to have Ngai stamp their travel documents to extend their stay illegally, the court was told.

When ICAC officers arrested Ngai at the control point on April 29, 2005, they found two other people's HKID cards in his locker.

The ICAC earlier charged one of the Mainlanders with conspiracy to offer advantages to an officer of the Immigration Department and an immigration offence. He pleaded guilty and was jailed for seven months.

The Immigration Department also charged the six other Mainlanders for immigration offences and all were given jail terms.