Foreign Minister John Baird is unexpectedly set to resign from the federal Cabinet this week amid what sources said had been tensions with the prime minister's office.

Baird's imminent departure — confirmed by a source late Monday — will deprive the right-leaning Conservatives of a senior Cabinet figure and renowned campaigner in the runup to an election set for October.

Polls show Prime Minister Stephen Harper will most likely lose his majority in parliament and could even be thrown out of power.