The NDP leader will reiterate his opposition to what his party describes as "Stephen Harper's dangerous and controversial Bill C-51" at a news conference in Robson Square, just steps from where hundreds of protesters gathered last weekend as part of the cross-country "day of action" against the bill.
Mulcair will be flanked by former BC provincial court judges Carol Baird Ellan and Bill Sandhu, who are both slated to run for the New Democrats during the next federal election.
The bill will likely be back in the political spotlight when MPs return to Ottawa next week.
The House public safety committee is currently reviewing the legislation, and is expected to meet twice daily until Friday in order to hear from more than 50 expert witnesses.
The New Democrats, the Official Opposition in the Commons, have vowed to vote against the bill when it returns to the House in April.
The federal Liberals, meanwhile, have indicated that they will continue to support it despite concerns over the failure to increase independent oversight.
Quebec concerned by new CSIS powers
The proposal to expand the mandate of Canada's spy agency to monitor and "disrupt" potential extremist threats has also raised the official ire of the Quebec government.
Earlier this week, three provincial ministers sent a highly critical letter to their federal counterparts in which they laid out their concerns with the bill, particularly the "vast powers" the bill will give the Canadian Security Intelligence Service.
"It is worrisome that the bill gives CSIS such vast powers, including the possibility to take certain actions that violate the Canadian Charter of Rights and Freedoms and Canadian law," the letter reads.
Additionally, the ministers say, more oversight is required to ensure the new CSIS powers are used only for their legally intended purpose.
The Quebec ministers also criticized Ottawa for not consulting with Quebec on the bill.
In response, a spokesman for Public Safety Minister Steven Blaney said he was "pleased to receive support from the Quebec government on the new measures aimed at ensuring public safety from violent extremism," and pledged to "continue to maintain a dialogue" with his provincial counterparts.