Former Singapore Civil Defence Force (SCDF) chief Peter Lim Sin Pang is guilty of corruption.

The 52-year-old was on Friday handed a guilty verdict by District Judge Hamidah Ibrahim, who ruled that Lim had been the one who initiated sexual encounter with Ms Angie Pang Chor Mui, whom he was not in an intimate relationship with.

And since he was a high-ranking civil servant with years of experience in public service, he should have know that he would contravene government procurement rules by calling her about radiation portal monitors, said Judge Hamidah.

"If he did not know that, then he has certainly made a wrong career choice in the last 25 years," she added.

Lim is accused of obtaining oral sex from Ms Pang in exchange for furthering the business interests of her then employer Nimrod Engineering,

The sexual encounter is said to have happened in the car of the former Nimrod sales director on May 2, 2010. Ten months later, Lim tipped her off about the SCDF's need for radiation portal monitors following the tsunami and nuclear disaster in Japan.

Nimrod eventually participated in the tender when it was called in April 2011.

The judge said that Ms Pang, 49, must have considered that if she did not perform oral sex on Lim, their friendship might be jeopardised, or it may affect Nimrod's business with the SCDF, and hence Lim had made her "an offer she could not refuse".

The judge also found Lim's credibility wanting as there were multiple inconsistencies between his statements to anti-graft officers and his evidence in court, making his claims during the trial "seriously questionable".

Lim will be sentenced at a later date. Under the Prevention of Corruption Act, he faces a maximum of five years in jail, a fine of up to $100,000, or both.