A leading French union, the CGT, has denounced last month's court decision in New Caledonia which gave 23 members of the mainly Kanak USTKE union jail terms of up to a year over last January's clashes with police in Noumea.
The CGT has issued a statement, warning the government against possible violence that may ensue as a result of the convictions.
Among those sentenced is the USTKE leader, Gerard Jodar, who was given a six-month jail term for directing striking workers during a prolonged fight near a bus depot at the centre of a strike.
The CGT says local bosses have found a powerful ally in the French high commissioner who tries to silence the USTKE union with violent police interventions.
It says Mr Jodar has been given a jail sentence for nothing else but being in charge of the union headquarters.