Tom Mulcair is pressuring the federal government to disclose documents pertaining to allegations that the judicial process surrounding patriation of Canada's Constitution was tainted by political interference.
The NDP leader is seeking the support of other parties to demand full disclosure after a search of Supreme Court records came up empty.
Mulcair says Canadians have a right to know whether the integrity and independence of the top court was compromised.
But the Harper government says it has no interest in re-opening what it calls old "constitutional battles."
And Liberal MP Stephane Dion says Mulcair is being "completely irresponsible," playing the game of separatists who are using the allegations to undermine Quebecers' confidence in Canada, its top court and its Constitution.
A new book claims documents obtained under the United Kingdom's freedom to information legislation show two Supreme Court justices engaged in backroom discussions with British and Canadian politicians about the court's deliberations on the legality of patriation.