A number of policy holders of Prudential Assurance Company Singapore yesterday got a rude shock when they found out their bank account had Giro deductions in excess of their insurance premiums. Some amounts were in excess of bank balances, resulting in failed Giro deductions.

Prudential said in a statement late last night that these erroneous deductions arose from a "technical glitch".

In a separate statement, the Monetary Authority of Singapore (MAS) said that the errors affecting customers of multiple banks were due to an operational lapse, not a cyber attack.

No further explanations were offered. But feedback from an online forum alleged that some customers received calls from their banks querying them over certain deductions. One policy holder in the forum said that his premium was $168 but Prudential had sought to deduct $16,800 from his bank account.

MAS has directed Prudential and their payment bank, Standard Chartered Bank Singapore, to effect the return of customer funds without delay, to keep customers updated, and to investigate the root cause of the incident.

"We take a serious view of such operational lapses and will take follow-up supervisory measures where appropriate," it said.

In its statement, Prudential said that a number of its customers experienced a Giro deduction in excess of their insurance premium or a failed Giro deduction.

It said that it is working with its banking partner to credit the relevant amount deducted back to its customers' accounts within the next 24 hours.

"Any interest lost will be refunded and any erroneous charges will be reversed as soon as possible," it added.

Affected policy holders may contact Prudential's customer hotline on 1800-333-0-333.

The insurance company also said that it would be posting updates on its Facebook page and website. "We are very sorry for the inconvenience caused," it said on Facebook.