Forty-seven people were killed and most of the Quebec community's downtown was destroyed last July after a fuel-laden train derailed and exploded.
Marois said moving the rail line is the responsibility of the federal government.
She estimated the cost of relocating the train tracks at as much as $175 million.
"We're looking at Ottawa because rail transport remains their responsibility."
The PQ leader made the comments as she announced her party's candidate for the area's riding in the April 7 election.
A spokesman for Denis Lebel, the federal minister responsible for infrastructure and Prime Minister Stephen Harper's Quebec lieutenant, said Ottawa has "always been there for the residents of Lac-Megantic."
"We have made available $155 million to help the community, including $95 million for decontamination costs, $35 million to help the local economy and $25 million to help pay for emergency response," Benoit Fortin said in an email.
"We have no intention of getting involved in a provincial election. We will work with the government that Quebecers elect, based on our common interests such as the economy, job creation and long-term prosperity."
Marois acknowledged during her visit to the community that the federal government had agreed to go 50-50 with Quebec on the cleanup costs.
"We have shared the costs related to the tragedy in Lac-Megantic," she said. "Now for future development, in the current case, this (the rail tracks) falls under federal jurisdiction."
The total cost of the catastrophe is still being determined and the governments estimate it will be years before a final figure is reached.