 By-elections are elections held to fill seats in Parliament that fall vacant in between general elections, known as casual vacancies.In the past, the Government took the position that the Prime Minister had discretion whether or not a by-election should be called to fill a casual vacancy in an SMC, and could leave a parliamentary seat unfilled until the next general election.However, in the case of "Vellama d/o Marie Muthu v. Attorney-General" (2013), which arose from a vacancy in Hougang SMC, the Court of Appeal held that the Constitution obliges the Prime Minister to call a by-election unless a general election is going to be held in the near future.