(Reuters) -Singapore Post has appointed the CFO of its Australia business as group finance chief, the company said on Sunday, a week after dismissing its CFO and two senior executives for mishandling a whistleblower report.

Isaac Mah, who joined Singapore Post in 2019, most recently oversaw the sale of the company's Australia business to private equity firm Pacific Equity Partners.

The Temasek-backed company has said it will name a new group CEO in due course.

Singapore Post fired group CFO Vincent Yik last week, along with CEO Vincent Phang and its international business unit chief Li Yu, after they were found to be "negligent" in handling a whistleblower report.

The alleged misconduct reported by the whistleblower related to several employees who worked in the company's international e-commerce logistics parcels business.

Shares of Singapore Post have dropped 5.4% since the company announced the dismissals last week.

Temasek is the largest shareholder of Singapore Post with a 21.75% stake in the company, followed by Alibaba Investment with a 11.21% stake, LSEG data showed.

Phang and Yik have indicated they will "vigorously contest" the termination of their employment.

They said in a joint statement on Tuesday that after the whistleblowing report was submitted, Singapore Post management did not take part in the investigation as set down in the company's whistleblowing policy.

The duo were asked for their views on the incident on March 11 and April 3 and responded accordingly based on the facts provided to them at that time.

But they only became aware of the full facts on April 27 following investigations by the external forensics team, they added.

"A significant majority of the shipments in question were linked to destinations where there were known issues - such as conflict zones (for example Israel).

"It was therefore important to establish the financial impact prior to communicating with the customer as well as determining any wrong doing by junior staff members."

Phang and Yik added that the management was briefed on the external forensic team's "conclusive" findings. The duo then agreed with and followed the instructions of the board.

"A settlement with the customer was then concluded that did not have a material financial impact," they said, adding that details of their full responses were submitted to the board on Nov. 22.

Phang and Yik's statement did not disclose the identity of the customer.