The ASIC investigation was launched after Fairfax Media revealed that a former senior company manager had detailed the allegations in the Federal Circuit Court and comes after a detailed initial assessment of the claims by the corporate watchdog.

It is understood the company was recently notified of ASIC's probe, but Leighton Holdings has not informed the market of the development.

Leighton Holdings declined to comment.

The revelation comes just three years after Leighton was sanctioned by ASIC for failing in 2011 to fully reveal the extent of its financial position, causing massive sharemarket losses and a class action law suit that cost the firm $70 million.

The firm is now facing multiple investigations, including a federal police probe into allegations the company paid foreign officials bribes and a second ASIC inquiry into accounting irregularities linked to the firm's joint venture with Indian company Welspun.

Indian police continue to pursue for questioning Bruce Munro, who runs Leighton's mining arm Thiess, over separate allegations – denied by Mr Munro and Thiess – that the firm defrauded Indian businessman Syam Reddy.

Labor Senator Sam Dastyari has also announced a Senate inquiry into foreign bribery by Australian firms that he has flagged will probe allegations Leighton Holdings paid kickbacks and engaged in corruption in the Middle East and Asia.

Leighton recently flagged its intention to change its name, in a move widely viewed by the business community as a recognition by the firm's majority Spanish owners that its scandal-ridden past has badly damaged the Leighton brand.

However, the latest ASIC probe relates to alleged misconduct involving members of Leighton's existing management team.

Fairfax Media revealed earlier this year that Leighton's former senior technical manager Alan Henry has alleged in the federal circuit court that Leighton's chief operating officer Adolfo Valderas Martinez and other top executives have been publicly overstating revenue "for fear" that disclosing adverse results "would jeopardise the company's reputation and financial position".

Mr Henry, a 20-year Leighton veteran, has also alleged that a number of Leighton executives had "suffered extreme stress and anxiety as a result of pressures to falsify or improve inaccurate reporting figures".

The allegations are detailed in an unfair dismissal case lodged in November by Mr Henry. He says he was pushed out of Leighton after repeatedly urging Mr Valderas and other senior figures to disclose unflattering financial figures.

Mr Valderas was appointed Leighton's chief operating officer in October 2013 ahead of a $1.1 billion takeover by Spanish construction company Grupo ACS in March 2014.

ACS, which controls 70 percent of Leighton, fired Leighton's chief executive and chief financial officer in March last year, appointing former ACS executive Marcelino Fernandez Verdes as CEO and chairman.

Mr Henry has sworn that Mr Valderas knew of major project blow-outs but "intentionally chose to disregard their significance".

Among the evidence Mr Henry has presented to the court is a photo of a whiteboard used during a management meeting in Perth in February last year. The photo allegedly shows a $205 million blow-out on the Chevron Gorgon Jetty Project, to $2.893 billion from $2.688 billion.

Mr Henry said that when he raised the issue of under-reporting on the jetty project at another meeting in March 2014 with Mr Valderas and Leighton Contractors managing director Craig Laslett, and questioned whether it should be disclosed to the Australian Securities Exchange, his observations were "not favourably received".

"The issues raised were a major concern for Mr Valderas and the Company, particularly in light of the recent change of control and their desire to develop a good reputation."

During another high-level meeting, Mr Henry said executives discussed how Leighton should retrieve $1.464 billion from the client on the jetty project, given it had only approved payments of $1.428 billion to Leighton and had rejected most of the additional claims already submitted.

Mr Henry said that during a later meeting with Mr Valderas in April 2014, it became clear that the firm had relied on "a knowingly false forecast" of $2.688 billion relating to the Gorgon project

Mr Henry has alleged he was "concerned" by this as the "number was ... used to uphold the first-quarter results publicly issued by Leighton Holdings."

Australian listed companies are required by law to give continuous and honest disclosure to the market so their shareholders are fully informed of the financial position.

Mr Henry has also alleged the company relied on "a total of around $4 billion" in revenue that its clients had not agreed to pay, did not know about or would most likely dispute.

He has alleged this "unapproved revenue" stemmed from an oil pipeline project in Iraq, a Hong Kong Kowloon rail terminus project, the Chennai to Nashri Tunnel project in India and the Chevron Gorgon Jetty project.

Mr Alan said he sought to "avoid the victimisation that his previous colleagues had suffered [in questioning the failure to act on cost blow-outs] by raising the issues with Mr Valderas on a number of occasions with the hope that the issues would be addressed."

"However, in raising these concerns, the Applicant received significant push back from Mr Valderas and the management team, for fear that such results would jeopardise the company's reputation and financial position," the legal claim states. "Not only was Mr Valderas aware of the shortfalls but he also intentionally chose to disregard their significance despite the several number of times the applicant raised them."

The court files state that Mr Valderas has previously rejected Mr Henry's claims, but Leighton declined to respond to questions.