SYDNEY, June 5 (Reuters) - Australia's corporate regulator said on Friday it had launched a formal investigation into three KPMG Australia partners linked to whistleblower allegations the accounting firm misused confidential client data to win lucrative audit contracts.

The Australian Securities and Investments Commission said it began a preliminary probe into KPMG in April and moved to a formal investigation after the resignation of the firm's CEO and audit chief last week.

"We have commenced our formal investigation earlier this week and I should also make clear that we have issued multiple compulsory notices throughout that period to KPMG," ASIC Chair Sarah Court told a Senate committee on Friday. 

"There are three registered company auditors that are currently within the scope of what we were looking at, but I have to say this is an ever-moving feast at the moment as more information comes our way. So I don't know that will be the end of it."

KPMG did not immediately respond to a request for comment.

In March, ​Deborah O'Neill, a senator from Australia's ruling Labor party, shared with parliament a whistleblower's allegations of misconduct at KPMG. They included that confidential board papers from real estate company Lendlease were used to support bids for major audit tenders for Westpac, a large bank, and Dexus, a property firm.

KPMG had conducted an internal investigation into the claims but failed to substantiate any misconduct. It has since engaged law firm Allens to conduct a new external investigation.

Court said she had "deep concerns" over the alleged misconduct. But ASIC did not have powers to regulate the firm due to its partnership structure, only individual auditors, she said.

ASIC CEO Scott Gregson added the corporate watchdog had also sought assurances from KPMG that no partners linked to the scandal were involved with the regulator's own active contracts with the firm.

KPMG ran a whistleblower service for the Reserve Bank of Australia under a contract that cost A$10,000 ($7,121) a year, the central bank's Governor Michele Bullock said on Thursday.

"I don't think we'll be reappointing them to the whistleblower service," she said in a Senate committee hearing.

A separate contract with KPMG for arranging foreign employee recruitment would also be re-tendered, Bullock said.

($1 = 1.4043 Australian dollars)