Quebec has long argued that the sector is of provincial jurisdiction under the Constitution.
"Regulation of securities trading is too important a matter to run the risk of its hinging, in whole or in part, on legislation whose legal basis is potentially unconstitutional," Justice Minister Stephanie Vallee said in a statement Tuesday.
"Given this new attempt by Ottawa to set up a pan-Canadian commission, Quebec needs to apply to the Court of Appeal once again."
Ottawa has long championed the idea of a national regulator, but the Supreme Court sided with the provinces in 2011 on who had jurisdiction. However, in its ruling the top court left the door open to federal-provincial co-operation.
In April, Yukon became the first territory to sign up for the planned national regulator, with the federal Finance Department saying at the time it was joining British Columbia, Ontario, Saskatchewan, New Brunswick and Prince Edward Island.
But the key jurisdictions of Alberta and Quebec have refused to join the national regulator.
If implemented, the co-operative national body would be expected to help oversee stock markets by policing abuses and securities fraud.
It would also administer a single set of regulations under the proposed rules and be funded through a single set of fees.
Canada currently is the only G20 country without a national securities regulator.
Under the current system, all 13 jurisdictions in Canada regulate their own capital markets and bond and securities issuances, although all except Ontario also belong to the so-called passport system by which the approval of one commission essentially allows for registration in another province.
Quebec argues the proposed plan would give Ottawa a veto within the body responsible for administering the scheme.
"This plan would adversely affect the maintenance of Quebec's expertise in securities, a key sector of our economy," Quebec Finance Minister Carlos Leitao said in the same statement.
"Moreover, the existing harmonized and collaborative securities regulatory system, set up by the provinces and territories, has been very successful in achieving investor protection and economic development objectives."
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