Wads of cash, a hot rod and free air travel have emerged as the latest kickbacks given to union officials and company managers, as the federal government moves to order a royal commission into union corruption.

Amid growing political despair at police and regulatory failings to tackle building industry corruption, Fairfax Media can also reveal that:

■ The kickback scandal has spread to a second building union, with former plumbing union national president Tony Murphy implicated in a kickbacks for contracts racket.

■ Convicted terrorist Khaled Sharrouf has been linked to the Sydney gangland violence that erupted over attempts by criminals to collect a disputed $9 million construction industry debt from billionaire property mogul Harry Triguboff.

■ A building company owner has alleged he was encouraged by a senior CFMEU official to become a major sponsor of the South Sydney Rabbitohs in return for ''beneficial'' backing by the union for job tenders.

■ The CFMEU is seeking to urgently interview building union whistleblower Brian Fitzpatrick about his claims he received a death threat from a colleague after he fought against the union's support of a crime figure.

Fairfax Media can also reveal that building union organiser Terry Kesby wrote to the NSW CFMEU last September warning it that Mr Fitzpatrick's whistleblowing had prompted a campaign to ''assassinate'' Mr Fitzpatrick's character and force him out of the union.

''If a rope was available, he [Fitzpatrick] would have been strung up over the tree in the car park," Mr Kesby warned.

On Friday, the CFMEU asked Mr Fitzpatrick to be interviewed as part of an internal union corruption probe being run by barrister Tony Slevin.

The fresh cases of kickbacks and bribery uncovered by Fairfax Media involve construction companies in NSW, Victoria and Queensland and are in addition to the kickbacks and corruption revealed last week by Fairfax Media.

Among the newly implicated companies is the Lack Group, which provides labour hire and traffic management services in NSW and Queensland.

A leaked letter written by CFMEU national secretary Michael O'Connor states that the union has asked Mr Slevin to investigate allegations made by a second union whistleblower that the Lack Group ''paid for'' a NSW CFMEU official and his family to stay on the Gold Coast in return for getting union support.

The internal inquiry will also probe allegations that the Lack Group provided other inducements to CFMEU officials, including ''funds … not properly accounted for''.

Sources aware of Lack Group's operations have confirmed that the company provided expensive gifts, hospitality, flights and cash bribes to a small number of CFMEU officials in an effort to win union support in winning contracts. The Lack Group refused to comment.

The new revelations of kickbacks aren't restricted to union officials.

Documents seen by Fairfax Media implicate a senior manager from the large civil construction firm Winslow in receiving bribes worth at least $60,000 in return for rigging multimillion-dollar contracts and leaking tender details to subcontractors.

The bribes include cash payments and luxury goods, including a hot rod. The implicated manager did not respond to phone calls while a Winslow spokesman said the company was satisfied no corruption had occurred. It is understood Winslow has conducted no forensic or independent investigation into the manager's alleged corruption.

Winslow has won major civil works projects, including road and sewerage building and maintenance contracts, at urban fringe developments in Victoria.

In a further widening of the scandal, Fairfax Media can also reveal that the former national president and Victorian assistant secretary of the Plumbing Trades Employees Union, Tony Murphy, sought kickbacks from several subcontractors in return for helping them win work on sites across Victoria, including the state's massive desalination plant.

It is understood that law enforcement agencies have evidence that Mr Murphy demanded payments as part of a cash-for-contracts racket.

Senior plumbers' union officials in Victoria removed Mr Murphy from his role in early 2012, after hearing allegations of his improper behaviour. However, an internal audit later commissioned by the union was unable to verify the concerns about Mr Murphy, who could not be reached for comment.

Mr Murphy was one of several senior building unionists who developed close ties to underworld figure and union "fixer" Mick Gatto.

In 2008, Mr Gatto helped to broker a $1.5 million Melbourne land deal between the plumbers union and a developer the underworld figure represents, the Banco Group.

Mr Gatto confirmed the arrangement, saying: "The plumbers [union] are friends and I do work for Banco. Certainly I made a phone call and I put them together [to do the land deal]," he said. The land was used to build a ''green'' plumbing training industry centre.

Fairfax Media is not suggesting the land deal was corrupt. But some senior union figures have queried the wisdom of using plumbers union members' money to finance a deal with a Gatto-linked company.

The corruption and organised crime scandal enveloping the construction industry has prompted federal cabinet members to question why Australia's policing and regulatory agencies aren't combating the industry's problems. Senior police privately say that additional government support is needed to finance the complex and resource-intensive investigations needed to break the industry's code of silence.

Victoria Police assistant commissioner Stephen Fontana has defended his force's handling of scandal.

NSW detectives are gaining more intelligence into the role of organised crime in the building industry through gangland murder probes.

Police are also probing whether convicted terrorist Khaled Sharrouf, who recently fled Australia on a false passport, was among several crime figures involved in efforts to collect a disputed $9 million construction debt from property developer Harry Triguboff.

Mr Triguboff and his company Meriton have no connection to the underworld violence that erupted last year in connection to attempts to obtain the funds, which a Sydney building firm owner claims he is owed.

The building firm owner was taken in for questioning by the NSW homicide squad last week, only minutes after he met with Fairfax Media.

''It's [the involvement of organised criminals and the violence] got nothing to do with me,'' he said. ''And the police believe that, too.''

The building company owner had met Fairfax Media to raise allegations about being approached by senior CFMEU officials in 2006 and told he would receive ''backing for jobs everywhere'' if he agreed to sponsor the then struggling South Sydney Rabbitohs.

He said he gave $130,000 in sponsorship funds to the club. In return, he says CFMEU officials ''thanked'' him by helping him secure a contract for a large development in Sydney's eastern suburbs. The CFMEU has dismissed the allegations.

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