Australia's competition regulator said it had asked ANZ Group...

Australia's competition regulator said it had asked ANZ Group (ANZ) to further justify the public benefits of its proposed A$4.9 billion ($3.32 billion) takeover of rival Suncorp's (SUN) banking business ahead of a formal decision on the deal's future.

The Australian Competition and Consumer Commission (ACCC) on Tuesday asked both parties to submit more information before a final ruling is delivered by June 12.

ANZ, Australia's fourth-largest bank by market capitalisation, last July announced plans to buy the banking arm of the Queensland-based regional bank and insurance group Suncorp to help grow its mortgage book.

The deal requires ACCC approval and sign-off from the Queensland government and Australia's federal treasurer.

In a report published Tuesday, the ACCC said its preliminary view was the information it had was insufficient to substantiate the "nature, likelihood and extent of the claimed public benefits, including ANZ's estimates of future synergies that will be achieved".

ANZ said when the deal was announced buying Suncorp's banking arm would boost its mortgage book by A$47 billion to A$307 billion and help it reclaim market share lost to its main competitors.

"Any acquisition of a potential rival by one of the major banks must be closely considered," ACCC deputy chair Mick Keogh said in a statement separate to the report.

Australia's banking industry is dominated by four large banks, including ANZ.

Suncorp said in a statement that it would provide a comprehensive response to address the ACCC's concerns and the deal remained in the best interests of the company. Suncorp will become a pure insurance firm if the deal is completed.

ANZ did not immediately respond to a Reuters request for comment. ($1 = 1.4738 Australian dollars)