CFMEU 'engaged in blackmail, extortion'

Officials in Australia's main building union have engaged in conduct that could amount to blackmail and extortion, a royal commission has found.

Citing a catalogue of alleged misconduct, the inquiry into union corruption and governance found the officials of the Construction, Forestry, Mining and Energy Union sought to conduct their affairs with deliberate disregard for the law.

Evidence suggested there was a pervasive and unhealthy culture within the union, with its officials preferring to lie rather than reveal the truth and betray their organisation.

The inquiry devoted most of its interim report to the CFMEU, examining instances such as union's black ban of developer Grocon, apparently because the company refused to employ CFMEU shop stewards.

"The conduct undertaken by officers of the CFMEU has included conduct which may constitute the criminal offences of blackmail and extortion," the report says.

It also recommends that Commonwealth and state prosecutors consider charging the CFMEU with illegal cartel conduct and particular officials with making threats, obstruction of Commonwealth officials and making false statements.

During hearings, the union made no submissions on specific allegations, which the commission deemed unsatisfactory.

But it still has time: the commission's term has been extended to the end of 2016.