Australia’s biggest building union is set to be dragged before the Federal Court after the nation’s competition watchdog alleged that it conducted an illegal boycott of concrete from building products supplier Boral across dozens of sites in Melbourne.

In its latest announcement, the Australian Competition and Consumer Commission (ACCC) said it had launched Federal Court action against the union, its Victorian branch and its Victorian State Secretary and Assistant Secretary John Setka and Shaun Reardon over secondary boycott action targeted at the building products maker which followed Boral’s decision to continue to supply concrete to Grocon sites whilst the CFMEU was in dispute with the builder.

In a statement, the ACCC alleged that over a twelve month period between February 2013 and April 2014, the union and its bosses instructed shop stewards to ban the use of Boral concrete at twelve commercial construction sites across Melbourne, and that the stewards subsequently told Boral customers that use of its concrete was not permitted and that the union would conduct special time-consuming safety checks specifically on Boral trucks if Boral concrete was used on a job.

The competition regulator also accused the union and its bosses of trying to induce Boral – which is Grocon’s exclusive concrete supplier – to enter into an understanding not to supply concrete to Grocon and engaging in undue harassment and coercion of Boral in relation to the supply of concrete.

In a statement, ACCC Chairman Rod Simms said the rule of law must be upheld on construction sites.

“The ACCC considers unions have an important role in protecting the rights of workers and ensuring safe and productive work places,” Simms said.

“However, the ACCC will not hesitate to take action where it has evidence that unions or individuals have engaged in conduct which goes beyond what is reasonable to protect workers, and is deliberately targeted at damaging business.”

The latest moves follow similar allegations which have been heard in the Royal Commission into Trade Union Corruption, which is set to deliver an interim report next month.

Last Sunday, CFMEU National Secretary Dave Noonan described those claims as baseless and fuelled by ‘anti-union whitewash’.

Simms says the ACCC has conducted its own separate investigation independent of the Commission.

The allegations relate to twelve sites at Deer Park, Officer, Port Melbourne, Hawthorn, Tarneit, Richmond, Lilydale, Notting Hill, Williams Landing, Werribee and, in Flinders Street and Elizabeth Street in Melbourne CBD.

The regulator is seeking fines, declarations and injunctions against the union and its officials.

A directions hearing is scheduled for December 12.