Australian artificial intelligence data centre operator Firmus has abandoned plans to raise almost US$5 billion through a stock market listing after investors questioned its soaring valuation and ambitious expansion plans.

The Nvidia-backed company withdrew its application to list on the Australian Securities Exchange (ASX) on Friday, October 9, citing market volatility and unfavourable conditions.

Firmus planned to offer shares at A$11 each, valuing the company at approximately A$44 billion (US$30.6 billion), nearly triple its August valuation. The offering would have been Australia's second-largest initial public offering, behind Telstra's 1997 listing.

UniSuper chief investment officer John Pearce, whose fund declined to participate meaningfully in the offering, questioned the company's valuation.

"We think that Firmus indeed has a compelling story. It just doesn't have a compelling valuation," Pearce said in an investment update released this week.

Pearce also warned that Firmus would require substantial additional borrowing and investment to finance its expansion.

Investor concerns intensified following the breakdown of Firmus's partnership with CDC Data Centres, an Australian operator of secure data centres. The companies had proposed a data centre development programme worth up to A$73 billion, known as Project Southgate, to build AI computing facilities across Australia.

CDC said the companies' priorities had diverged as Firmus expanded into Asia. Firmus described the separation as mutual and said its existing development plans would not be affected.

Firmus currently operates two leased data centres in Melbourne and Singapore, with another five planned across the Asia-Pacific region. Its expansion depends on substantial investment in computing equipment and infrastructure.

The failed offering also affected Australian construction services provider Maas Group, which owns a 3.2% stake in Firmus. Maas shares closed 6.7% lower on Friday after plunging 22.4% on Thursday.

Firmus now intends to pursue private funding while considering alternative public-market options, including a possible overseas listing.

Reuters reported that a future listing on the US Nasdaq exchange was under consideration, although Firmus declined to confirm those plans.