The militant Victorian construction union has signalled its members may start wearing body cameras used by police on the same day the building construction watchdog launched a landmark prosecution against the union for alleged unlawful picketing.

The court action is the first time Australian Building and Construction Commission has used unlawful picketing provisions with significantly higher penalties than were available under previous legislation.

The ABCC alleges the Construction, Forestry, Mining and Energy Union (CFMEU) and three of its representatives allegedly blocked access to two Melbourne building sites in May last year. Cold storage company Newcold has two sites at which the union was alleged to have prevented office staff, subcontractors and workers from entering or leaving on May 8.

CFMEU Victorian officials John Setka (C), and Shaun Reardon (R) outside Melbourne Magistrates Court Credit:Joe Castro AAP

Maximum penalties for a breach under the Building and Construction Industry (Improving Productivity) Act 2016 are more than three times as high than previous fines at $210,000 for bodies corporate and $42,000 for individuals.