The head of the construction union embroiled in corruption claims says bikies could be working within his organisation, but there's nothing he can do about it.

A joint ABC-Fairfax Media investigation claims union officials are making corrupt deals to help companies linked to organised crime secure construction contracts.

Bikies are also alleged to have been called in help secure these contracts.

Dave Noonan

CFMEU construction division national secretary Dave Noonan

Construction, Forestry, Mining and Energy Union (CFMEU) national secretary Dave Noonan says there are about 100,000 members in his union.

“Some of them will inevitably be members of motorcycle clubs, and some of those clubs may be, if you like, outlaw motorcycle clubs,” he told the Nine Network on Wednesday.

He said the union will sack anyone who has acted corruptly, but can’t fire someone just for being a bikie.

“The union does not have the ability or indeed the desire to interrogate everybody about their associations,” he said.

The latest revelations about alleged bribery and corruption in the trade union movement has bolstered calls for a royal commission and the return of the Australian Building and Construction Commission (ABCC).

Victoria’s desalination plant and Sydney’s Barangaroo South development are among a number of projects with which companies connected to major crime figures are reportedly involved.

Mr Noonan, however, stressed that the police are best placed to investigate such claims.

“I think that the proper place to test the truth of allegations is through a full police investigation and a court process,” he said.

He noted that past allegations made by the ABCC a few years ago proved to be false after court proceedings.

He has also found no basis for recent claims of corruption on the Barangaroo site.

“I have been unable to find any evidence,” he said.

Former CFMEU official Brian Fitzpatrick also told ABC’s 7.30 on Tuesday that he received a death threat from another union organiser for raising concerns about union corruption.

But Mr Noonan said both the union and police investigated that allegation and found it couldn’t be substantiated.

“I would urge everybody to treat his words last night with great caution,” he said.

ACTU President Ged Kearney said she’s 100 per cent confident in Mr Noonan’s leadership.

“They are handling this very well,” she told Fairfax Radio.

 “These are sensational allegations that haven’t been proven.”