The Australian Building and Construction Commissioner alleged the official told the company director the business would not receive a plumbing contract unless they signed a union EBA, saying “you will sign, we will force you to sign”.

“We will force the builders not to take you on their works,” he allegedly said.

“Because these jobs will be up in the country we will put so much pressure on them in the metro area it won't be viable for them to take you.”

The company director asked: “Are you holding a gun to my head?" to which the union official allegedly said “Take it whatever way you want”.

But on Friday Federal Court Justice David O'Callaghan ordered the proceedings be dismissed.

“I am unable to accept that the applicant has proved, to the standard required, that the [union organiser] made the disputed threats,” he said.

“I am, on the contrary, of the view that he did not make those disputed threats.”

Plumbers union state secretary Earl Setches said the organiser had been “dragged through the courts with the threat of a penalty hanging over his head just for doing his job”.

“We’re very happy that the court has vindicated him and the union in this decision,” he said.

“Every day that our organisers spend in court defending themselves from these prosecutions is a day they can’t be on site doing their job.”

In his judgement, Justice O’Callaghan described some actions of the ABCC investigator as “not easy to fathom”, a finding lawyer Daniel Victory – who represented the union and the organiser – said raised “serious questions about the ABCCs investigation processes”.

“Unions play a critical role in making workplaces safe and improving pay and conditions of working people. It’s important that union organisers can go about their work without having to worry about being prosecuted for doing their job,” he said.

“This ABCC has obviously spent a lot of money on this case, meanwhile, countless victims of wage fraud from places like 7-Eleven have been turned away by the government due to lack of resources. It’s hard to understand how there’s enough money for cases like this but not for victims of wage fraud.”