Australia’s largest construction union has been convicted and fined $1.25 million in a landmark Supreme Court decision for its role in stopping work at Grocon’s Emporium project in central Melbourne.

Already the fines for criminal contempt against the Construction, Forestry, Mining and Energy Union (CFMEU) for the blockade in August and September 2012 are some of the heaviest against a union.

Financial damages for Grocon are yet to be determined with separate cases ongoing.

Supreme Court justice Tony Cavanough said ‘‘the pattern of repeated defiance by the CFMEU’’ in this case and previous cases was ‘‘very troubling’’. He said the nature of the union’s defiance of the court orders meant he found it in criminal contempt.

‘‘I regard these contempts as exceptionally serious,’’ he said.