The Maritime Union of Australia has been put on the spot after its Scandinavian counterpart announced it would refuse to unload 3000 tonnes of toxic waste bound for a Danish port from Botany Bay.
The Australian union is understood to be debating whether its members should refuse to load the 252 shipping containers on to the ship.
Danish, Norwegian and Swedish dock workers have agreed not to touch the cargo of hexachlorobenzene, a byproduct of solvents manufactured in Botany until 1991.