UK Parliamentary Vacancies
If a seat became vacant in the UK Parliament the Speaker of the Commons would issue a warrant, which would be followed by the issue of an election writ. During a parliamentary session the warrant is issued following a motion in the House of Commons. If a vacancy occurred after a new parliament (straight after a general election) the warrant would not be issued until the time for bringing an election petition had passed. If a writ is pending the warrant will not be issued until the petition has been heard.
Current UK Parliamentary (Torridge & West Devon Constituency) Vacancies