ZURICH (Reuters) - Swiss financial market regulator FINMA ordered an audit into Credit Suisse's handling of events leading to its demise in 2023, when the bank was acquired by its longtime rival UBS, Swiss newspaper SonntagsZeitung reported on Sunday.

According to the paper, FINMA is looking at the 15 months prior to the state-orchestrated merger in March last year, for which purpose it said close to a dozen current or former employees of the two banks had been interviewed.

To carry out the audit of the crisis management at Credit Suisse, FINMA had commissioned law firm Wenger Plattner, which conducted the interviews, the paper reported.

That appointment followed what the paper said was a "secret" order issued by FINMA in September 2023 informing the banks that it wanted to review how Credit Suisse handled the crisis. The interviews of the staff should show whether authorities had been misled by Credit Suisse's then-management, the paper said.

FINMA and Wenger Plattner, the Swiss finance ministry and the Swiss National Bank did not immediately respond to Reuters requests for comment. UBS declined to comment.

The investigation encompasses questions such as when it became clear Credit Suisse could no longer be saved, what the bank's liquidity was like, how its equity was looking and how its management was in general, the newspaper said.

In a report issued in December, FINMA said Credit Suisse came close to imploding months before its takeover and argued for stronger powers to oversee banks.

A Swiss parliamentary committee that has been investigating how authorities handled the demise of Credit Suisse is expected to deliver its report later this year.

Swiss authorities in April set out a package of measures - including stricter capital requirements for UBS - aimed at preventing a repeat of the Credit Suisse meltdown.

Parliament is expected to debate those proposals following the publication of the parliamentary report.

Critics of the Credit Suisse takeover argue that Swiss authorities could have kept the bank going as a separate business but were slow to act and should have given greater assurances that it would survive.

The authorities have defended their actions, and pointed to failures at Credit Suisse for the collapse.

(Reporting by Dave Graham; Editing by Emelia Sithole-Matarise)