Government Chief Whip, Patrick McLoughlin, moved the Writ for the Belfast West by-election on Monday 16 May.
The moving of the Writ follows the appointment of Gerry Adams to the office of Steward and Bailiff of the Manor of Northstead on 26 January 2011. A by-election will take place in the Belfast East constituency.
How an MP vacates their seat
A resolution passed by the House of Commons on 2 March 1624 prohibits MPs directly from resigning their seats. Death, disqualification and expulsion are the only means by which a Member’s seat may be vacated during the lifetime of a Parliament.
An MP who wishes to resign has to go through the process of applying for a paid office of the Crown, which automatically disqualifies the MP from holding a seat in the House of Commons. There are two offices which MPs can apply for, Crown Steward and Bailiff of the Chilterns Hundreds and of the Manor of Northstead.
An MP wishing to resign applies to the Chancellor of the Exchequer for one of the offices, which he or she retains until the Chancellor appoints another applicant or until the holder applies for release from it. (Every new warrant issued revokes the previous holder). It is usual to grant the offices alternately; as this enables two Members to retire at precisely the same time.
The House of Commons Information Office factsheet on The Chiltern Hundreds provides more information on the history of the Chiltern Hundreds. A Parliamentary Information List provides information on who has been appointed to the Chiltern Hundreds since 1850.