Criminal charges against two men accused in the Lac-Mégantic tragedy should be dropped, their union and lawyers argued Thursday.

Train engineer Tom Harding, railway traffic controller Richard Labrie and Jean Demaitre, the manager of train operations, are each charged with 47 counts of criminal negligence causing death — one for each victim of the July 2013 train derailment.

A conviction carries a maximum life sentence.

Harding and Labrie are members of the United Steelworkers union, while Demaitre is not unionized.

Union spokesman Daniel Roy and lawyers for Harding and Labrie say the charges should be dropped in light of the Transportation Safety Board of Canada's final report into the tragedy.

In last week's report, the TSB criticized the Montreal, Maine and Atlantic railway for its "weak safety culture" and also targeted Transport Canada for its poor oversight of railways, particularly amid a booming oil-by-rail industry across the continent.

"It should now be obvious that the charges against each of these workers no longer have their place," said lawyers Thomas Walsh and Marc-Antoine Cloutier.

"To continue along this path would not serve the public interest and would in no way help prevent such an incident from happening again."

Walsh is representing Harding, while Cloutier works for a legal clinic that is defending Labrie.

Walsh also called for a public inquiry into the tragedy, going so far as to say it would be more important than the long-running Charbonneau Commission looking into corruption in the construction industry.

TSB points to insufficient brakes

The TSB report said Harding applied an insufficient number of hand brakes on the train — seven — and conducted an inadequate test before he left the convoy unattended and retired to a local inn for the night.

Before he left the scene, Harding called MMA's rail-traffic controller to report mechanical problems on the locomotive and thick smoke belching from its exhaust. They agreed he could leave the engine for the night.

Later that night, a fire broke out on the locomotive. Firefighters called to the scene shut down the locomotive, which gradually disengaged the engine's air brakes.

An MMA track foreman with no background in locomotives met the firefighters at the scene and, after consulting the rail-traffic controller, they left without restarting the locomotive. Eventually, the train started rolling toward Lac-Megantic, where it derailed and exploded.

TSB chair Wendy Tadros has said, however, that the underlying causes of the accident go well beyond the number of hand brakes applied and the engineer's actions that night.

Back in court in September

The three accused were arraigned in Lac-Megantic last May. At the time, Walsh said Harding intended to plead not guilty to the charges and that the defence asked the court for a jury trial in the devastated community.

Several locals who watched the suspects enter the courtroom said they hoped authorities would eventually lay charges against railway and government officials.

The next court appearance in the case has been set for Sept. 11.

Quebec provincial police said recently the investigation remains active, which could lead to more arrests.