The construction arm of the Victorian branch of the CFMEU has been caught up in a cycle of “lawlessness”, where violence was accepted and threats substituted for negotiations.

This is one of the damning findings of an interim report into allegations the construction and general division was involved in criminal and corrupt conduct, as uncovered by Nine newspapers earlier this year.

The interim report prepared by Geoffrey Watson SC, who CFMEU National Secretary Zach Smith engaged in July to conduct an independent investigation into the allegations, was released on Monday.

Watson made seven recommendations, including that further investigations to identify instances when Victorian branch officials have engaged in or been subject to threatening, violent or abusive conduct be undertaken.

He also said the branch should build “cooperative relationships” with the Victoria Police, the Australian Federal Police and regulatory authorities “so that criminal conduct can be dealt with in accordance with the law”.

“Based on the information uncovered during my investigation, the Victorian Branch has been caught up in a cycle of lawlessness, where violence was an accepted part of the culture, and threats of violence were a substitute for reasoned negotiations,” Watson said.

Watson noted his investigation was hampered by his inability to compel witnesses to give evidence or compel the production of documents.

“I was unable to offer potential witnesses any promises of confidentiality,” he added.

“Part-way through my investigation, I was told that threats of violence had been made including against members of the executive team of the Victorian branch.

“Because of those threats, I was instructed to refrain from contacting certain third parties.”

Last month, federal Attorney-General Mark Dreyfus placed the construction arm of the CFMEU, and all of it branches. into administration.

Dreyfus appointed Mark Irving KC as administrator.

Watson said Irving later instructed him to provide his report and make recommendations about investigations the administrator should carry out.

Watson also recommended further probes into any remaining links between union delegates and outlaw motorcycle gangs, and their influence.