The federal Liberals say they will introduce a confidence motion in early October.
CBC News quotes Liberal Bob Rae as saying his party will vote against the minority Conservative government at the earliest opportunity.
It could come as soon as October 1.
But the loss of Liberal support doesn't mean Stephen Harper's minority government will soon fall or that an election will be called in the near future.
The government's survival will depend on how the NDP and Bloc Québécois respond to the Liberals' intentions.
The House of Commons will resume sitting on September 14.
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