Fairfax Media reported that former Leighton chief executive David Stewart resigned as chief executive of UK contractor Laing O'Rourke's Australian business yesterday, after he was named as one of the former Leighton bosses who allegedly knew of the company’s kickback methods to win overseas contracts.

It is understood he was also asked to resign as a member of the company’s global executive committee by Laing O'Rourke global CEO Ray O'Rourke over the weekend.

Former Leighton International boss David Savage stepped down from the board of UK engineering group Keller over the weekend, after his signature was found on a preliminary tender document that included an alleged $A42 million kickback to win a $750 million oil pipeline contract in Iraq.

He has been a non-executive director since August 2011.

A third former Leighton executive alleged to have known about bribery to secure contracts, Russell Waugh, also appears to be in trouble over the scandal.

Waugh is head of Australian construction firm UGL's $2.3 billion engineering business.

He was reportedly in talks yesterday with UGL chairman Trevor Rowe and chief executive Richard Leupen about whether he should keep his position.

It is understood Waugh has been at the job for only a month.

Leighton has taken no action against any of its employees or board members following last week’s bribery, corruption and cover-ups report by Fairfax reporters.

A six-month investigation by the media group uncovered hundreds of confidential documents showing the construction giant resorted to a series of shady tactics and multi-million dollar kickbacks to win contracts in Iraq, Indonesia, India and Malaysia.

The investigation suggested former Leighton CEO Wal King may have been aware of the bribery culture at Leighton International but King denied such claims last week.

In addition to being investigated by the Australian Federal Police, Leighton is facing court challenges from some of its shareholders.

The group faces a possible class action for allegedly failing to disclose allegations of bribery, corruption and investigated misbehaviour to shareholders who bought shares in the company in 2010-11.

The class action comes on top of a writ issued last Friday by the Supreme Court of Victoria against Leighton following the Fairfax report.

The writ alleges Leighton breached its continuous disclosure obligations in section 674(2) of the Corporations Act through its failure to disclose:

• Allegations of bribery and corruption involving senior officers responsible for a project in Iraq; and
• An investigation of misbehaviour involving senior officers including as the subject of a claim by Leighton against a former employee for $5.6 million.

Leighton Holdings issued a statement denying the basis for the alleged claims and said it would “vigorously” defend the class action.

On Monday the construction giant warned the media that coverage about matters currently the subject of the AFP investigation should be fair and balanced and must not resort to broad-based accusations of impropriety.

“Leighton does not propose to correct all of the inaccuracies contained in a number of media articles,” the company said.

“It is not appropriate for Leighton to descend to a debate over matters of fact and matters of error when those matters are the subject of investigatory and court processes.

“Notwithstanding the seriousness of the matters raised, Leighton takes exception to the sweeping criticisms of its governance structures, processes and integrity.

“Leighton’s board and management condemn any form of corrupt or fraudulent behaviour.”