Mandatory general election if a governing party changes leader

Background

I want legislation that forces a general election to be held if the leader of the governing party resigns during the government’s term in office.

Additional details

When governing parties get a new leader they do not have a country-wide mandate to govern. A fresh election each time a governing party changes leader will ensure that the new PM has democratic legitimacy. Ultimately the PM's authority should derive from the people rather than a faction of party members. Leadership contests held solely within a political party do not provide the public with a meaningful say in who governs the country and undermines public trust in government.