The Auditor-General's Office (AGO) has taken the Ministry of Health (MOH) to task for the way tens of millions of dollars were spent in the building of the $800 million Ng Teng Fong General Hospital.
The 700-bed hospital in Jurong was completed in 2015 - about half a year behind schedule.
The AGO's latest annual report criticised the ministry for "lack of controls and inadequate oversight" of the project.
The ministry said yesterday it will strengthen its project oversight processes and management controls.
But there was no wrongdoing, it added. "There was no indication of fraud or corrupt practices which warrant further investigation, or deliberate wrongdoing by the persons involved in the projects."
The AGO's report found that the ministry had paid $4.08 million for supervisory staff without ensuring that they were needed.
It was done although the ministry had already hired a contractor for $8.16 million to provide site supervisory services, it noted.
When asked about it by the AGO, the ministry said it was "not aware" its agent had separately hired site supervisory staff. It later told the AGO there was no duplication as the contractor's staff number fell by five, which corresponded with the five the ministry hired.
But this was incorrect. The AGO found that the contractor had cut only three, not five, workers. Also, it had hired six, not five, people, resulting in a net increase of three workers.
The ministry also paid one of the three people, who was "supposedly reduced" from the contract, for about two years.
In fact, the ministry was uncertain if it had to pay for the supervisory services after March 2015.
The AGO also flagged irregularities in seeking approvals when changes were made to the hospital contract. The changes involved $30.09 million. It said: "The lack of the required level of checks increased the risk of fraud."
There was "no assurance that MOH had exercised financial prudence in the use of public funds" or that the changes in the contract were scrutinised before approval was given, said the report.
The AGO also found lapses in approvals for 40 changes to contracts of 10 other projects that involve $3.76 million.
Approvals were either not obtained, sought after work had started or were submitted to the wrong authorities.
In some cases, approvals were obtained "before the relevant assessment and recommendations were made", the AGO said.
As a result, they cast doubts on whether the changes were properly assessed, it added.
The ministry said yesterday that it will work to "improve the competencies of our officers through more structured training on public procurement procedures".