Politics of the United Kingdom
The UK Parliament is the supreme legislative body in the United Kingdom (i.e., there is parliamentary sovereignty), and Government is drawn from and answerable to it. Parliament is bicameral, consisting of the House of Commons and the House of Lords. There is also a devolved Scottish Parliament and devolved Assemblies in Wales and Northern Ireland, with varying degrees of legislative authority.
By-election
By-elections are held in most nations that elect their parliaments through single-member constituencies, whether with or without a runoff round. This includes most Commonwealth countries, such as the United Kingdom, Canada and Pakistan, as well as non-Commonwealth countries such as France. In the UK a writ for a by-election must be issued within three months of a vacancy arising.