Why must a prime minister maintain support from a majority in the legislature?

In parliamentary systems, a prime minister must maintain the support of a majority in the legislature to remain in office because their authority is derived directly from that body’s confidence.12

This requirement is fundamental to the parliamentary system, where the executive and legislative branches are interconnected rather than strictly separated. The legislature possesses the power to remove a government through a vote of confidence, a procedure where members can issue a motion of "no confidence" or censure if they disapprove of the government's actions. If a prime minister loses this majority support—often demonstrated by a defeat on a major piece of legislation or a formal vote—they are typically forced to resign.23

Because the government's survival depends on this ongoing legislative backing, prime ministers generally rely on strict party discipline to ensure their supporters vote in alignment with the administration. This structure ensures that the head of government remains accountable to the elected representatives of the people throughout their tenure.32