Treasury chief Christopher Hui said officials are gatekeepers and must be accountable to the public in spending public funds, in light of the scandal involving the procurement of bottled water for certain government offices.

An Audit Commission report noted that human error was involved in the case, which saw the director of the firm supplying the water being charged with fraud in August.

Hui told a TVB programme on Sunday that the government has since strengthened due diligence checks and made clearer stipulations in work guidelines, so officials will make better use of their vetting power.

Hui had earlier said more than a dozen officials from the Treasury and the Government Logistics Department are subject to disciplinary investigation.

He told reporters that even if some of them have retired, that wouldn't affect the probe as it focuses on the matter itself, while reviewing the roles played by different officials and civil servants.

The audit review found that the Government Logistics Department allowed the firm to change the brand's name under contract, even though it was informed by the Hong Kong Standards and Testing Centre that water testing reports submitted weren't valid.

"There's a chance that colleagues felt there's a new situation, and hope this new contractor could understand government procedures more easily," Hui said.

"Therefore, in some respects, they might have handled this matter from more of a facilitator's point of view."