List of United Kingdom MPs by seniority (2005–2010)

The criteria for seniority, used in this article, are derived from the way that the Father of the House is selected. They are not laid down in Standing Orders but arise from the customary practice of the House of Commons.

The modern custom is that the Father of the House is the MP who has the longest continuous service. If two or more members were first elected in the same General Election (or at by-elections held on the same day), then priority is given to the one who was sworn in first. The order of swearing in is recorded in Hansard, the official record of proceedings.

When a member has had broken service, that does not affect his or her seniority (for the purpose of qualifying as the Father of the House) which is based on the latest period of continuous service.

The Sinn Féin members, who abstain from taking their seats at Westminster, have never been sworn in. They are ranked (in this list) after all other members who have taken their seats. Between themselves they are ranked by the first date of election, for the current period of continuous service. If that criterion is equal, then they are ranked by alphabetical order of surnames.

In the House of Commons, the sole mandatory duty of the Father of the House is to preside over the election of a new Speaker whenever that office becomes vacant. The relevant Standing Order does not refer to this member by the title "Father of the House", referring instead to the longest-serving member of the House present who is not a Minister of the Crown (meaning that if the Father is absent or a government minister, the next person in line presides).

Note: The effective Government majority was higher than the notional majority, because MPs from Sinn Féin did not take their seats due to their long-standing policy of abstentionism and vacant seats have no vote. Technically, the speakers belong to parties in a notional majority, though they do not usually vote and therefore don't figure in an effective majority.

This article assigns a numerical rank to each of the members elected in the 2005 general election and subsequent by-elections, except for those who were elected but never sworn in, who are displayed at the bottom without a number. Members shaded in pink ceased to be MPs during the course of the parliament.

• List of MPs elected in the 2005 United Kingdom general election