The Tax Practitioners Board (TPB) has escalated its scrutiny of KPMG, upgrading its ongoing review to a formal investigation.

The move comes as the regulator faces mounting questions about its independence, particularly regarding the conduct of its chair, Peter de Cure, who is a long-standing partner at KPMG.

De Cure, a 25-year partner at the accounting firm, has previously downplayed the severity of the audit leaks scandal, characterizing it as an internal human resources matter.

However, the decision to launch a formal investigation signals a significant shift in the regulator's posture, suggesting that the issues at hand extend beyond internal personnel disputes.

The escalation adds to a growing list of institutional concerns regarding KPMG's governance and audit practices.

The Reserve Bank of Australia (RBA) has already confirmed it is reviewing its professional relationship with KPMG Australia, marking a notable step in the broader regulatory scrutiny of the firm.