The PQ would crack down on English in the workplace and introduce stricter rules for who must attend French-language junior college, Marois said at a campaign stop in Montreal.
Marois said the province's landmark language law, Bill 101, must be updated to stop the decline of French in the province, in particular in Montreal shops and businesses.
The PQ leader, who criticized the Liberal government for failing to do enough to protect the French language, said she would introduce new legislation within 100 days of taking power that would close a loophole that allows companies to operate in English.
"I think we need to look over all of this, to see if there are gaps or corrections that need to be made," Marois said.
Recent polls have placed the PQ ahead of the Charest Liberals and the new Coalition for Quebec's Future in the election scheduled for Sept. 4.
The PQ's overhaul of Bill 101 would extend language rules to businesses with between 11 and 50 employees, making French the mandatory language in the workplace, Marois said.
Immigrants and francophones would also be required to attend a French-language junior college, known in Quebec as Cegep. At the moment, post-secondary students can choose to go to either a French or English Cegep. Those language restrictions already apply to high school and elementary school students.
Marois said the PQ would also review the rules that allow companies such as aeronautics giant Bombardier to deny employees the right to work in French.
Marois said it's normal that some tasks are performed in English when a worker is interacting with people outside Quebec, but within the province it shouldn't be the norm.
"Once (the employee) hangs up the phone, I think business in Quebec needs to happen in French," she said.
Marois has already promised to increase the number of language inspectors to monitor the presence of French on commercial signs.
The PQ also offered details Sunday of a party committee that's been meeting since February in an effort to develop a strategy for another referendum on sovereignty.
"The goal was to do as much as possible before we get to power," said Alexandre Theriault-Marois, head of the PQ's political committee.
Another meeting scheduled for this summer was cancelled due to the campaign, but will "undoubtedly be accelerated" should the PQ be elected to power, Theriault-Marois said.
The Charest Liberals, meanwhile, promised to introduce new legislation of their own.
Premier Jean Charest said a returning Liberal government would introduce legislation that would deny anyone facing "serious" criminal charges the right to bid on government contracts.
"We will ensure that public construction contracts are awarded to companies above all suspicion," he said.
If the new version of Bill 35 was in force today, companies linked to the empire of the businessman Tony Accurso — who is facing charges including fraud, breach of trust, and bribery — would be excluded from the process of awarding public contracts.
On Sunday, the Coalition for Quebec's Future also unveiled its complete election platform, a hefty document with 94 separate party pledges.
Among the new elements in the platform were major changes proposed to Montreal's municipal governance. Party leader Francois Legault said cutting down on the number of city councillors would give the city centre more decision-making power to improve problems like congestion.
The party, which promises to set aside the issue of Quebec independence, also promised to get tougher on crime.
- with files from Jocelyne Richer, Alexandre Robillard and Martin Ouellet
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