Auditors Ernst & Young are unable to sign off Tiscali's annual financial results, casting even more doubt over the broadband provider's future.
The professional services firm released a statement to the Milan stock exchange explaining that it is unable to provide an overview of Tiscali's 2008 performance.
Experts have refused to sign off the figures and suggested that it is uncertain whether the company can continue to operate unless current debt arrangements are renegotiated.
Ongoing discussions are taking place between the provider and its creditors, with Tiscali voicing disagreement with the Ernst & Young over the audit report.
"The company, in disagreement with the conclusion drawn by the audit report, believes that it has co-operated at best and that it has provided all the information necessary to enable the independent auditors to issue an audit opinion on its 2008 financial statements," the company said.
This is the latest piece of bad news for Tiscali, with the ISP revealing earlier this month that it failed to attract its target of 200,000 subscribers to its broadband TV service.
Elsewhere, Tiscali customers were left without email access over the Bank Holiday weekend after the provider neglected to renew its screaming.net domain name.