The by-election was prompted by the resignation of the constituency's Member of Parliament, Gerry Adams[1] in advance of his candidacy in the 2011 general election in the Republic of Ireland.

Under Section 4 of the House of Commons Disqualification Act 1975, if an MP wishes to vacate their seat, they can request appointment to either of two 'offices of profit under the Crown' which disqualify them from membership.

[7] Although David Cameron said during Prime Minister's Questions that Adams had "accepted an office for profit under the Crown", Adams denied this and received an apology from the Prime Minister's Office for not informing him of the procedure and for stating that he had applied for the "post".

[10] However, because Sinn Féin MPs do not take their seats in the Commons, the writ was moved by the Government Chief Whip, Conservative Patrick McLoughlin MP on 16 May 2011.

[13] Paul Maskey, a member of the Northern Ireland Assembly, won the Sinn Féin nomination.