A former construction boss testified at the Charbonneau Commission that Boisclair authorized a $2.5-million subsidy in 2003 for a project involving a company that had ties to the Hells Angels.
Boisclair was a PQ cabinet minister in 2003 when he gave the green light to the subsidy.
On Wednesday, Coalition member Jacques Duchesneau drew links between the criminal organization and the fact Boisclair has admitted to using cocaine before.
Boisclair, who is currently Quebec's delegate-general in New York City, warned he would sue Duchesneau if he didn't retract his comments.
But Duchesneau says he has no intention of withdrawing the remarks, while Coalition Leader Francois Legault is defending his member of the legislature.