SINGAPORE - A former higher Customs officer who helped four Indian nationals fraudulently claim almost $500,000 in goods and services tax (GST) via the electronic tourist refund scheme was jailed for five years on Thursday for tax evasion and corruption.

In sentencing Mohamed Yusof Abdul Rahman, 67, District Judge Lim Tse Haw felt that his overall culpability was higher than any of the accomplices, given the aggravating factors.

"Further, there is a need to impose a deterrent sentence in order to make it clear to all public servants that the courts will come down very hard on those who betray the public trust that is reposed in them to the detriment of the State and allow themselves to be corrupted in the process," he said.

Yusof who faced 136 charges had pleaded guilty to 25 GST charges and seven bribery offences which were committed over a one-year period.

The total amount of GST that he helped Sundar Panneer Selvam, 46, Baskaran Uthirapathy, 28, Pounraj Natarajan, 25, and Gobi Rahman, 31, evade amounted to $493,859. The total sum he received as bribes on 33 occasions was $11,400,

On Thursday, he was ordered to pay a penalty of $11,400 for corruption, and a penalty of $661,685 - three times the tax defrauded.

The court heard that while Yusof was deployed at the GST Refund Inspection Counter at Changi Airport, his duty was to process GST refund claims made by tourists leaving Singapore.

He helped to approve the four Indian nationals' GST refund claims even though the jewellery produced did not match the goods description on the receipts. In return, Yusof received bribes in cash.

Yusof is no longer employed by Singapore Customs after his employment contract expired last September.

The four Indian nationals were sentenced last October to jail terms of between 36 and 48 months and penalties amounting to three times the tax defrauded.

The case against a sixth man, goldsmith shop employee Lim Pheck Aun, 50, is pending.