Most select committee chairs are elected by the whole House in a secret ballot held after each general election and when a vacancy arises. The chairs of all the departmental select committees, as well as the chairs of the Environmental Audit, Petitions, Public Administration and Constitutional Affairs, Public Accounts, Procedure, and Standards Committees, are elected in this way. The chairs of the Backbench Business Committee, Standards and Public Accounts must come from the official Opposition.
The chairs of other committees are elected by the members of that committee. These include the chairs of the Administration, European Scrutiny, Finance, Liaison, Privileges and Committee of Selection and the chairs of any joint committees.
Once elected, chairs remain in post until the end of the Parliament if they choose to. The only exception is the chair of the Backbench Business Committee, who is elected at the beginning of each session.
There is a term limit on chairs: a committee can't have the same chair for more than two back-to-back Parliaments or a continuous period of eight years - whichever is longer. This rule doesn’t apply to joint committees. There are provisions allowing committees to remove a chair who’s been elected by the whole House. Chairs elected by the committee can be replaced by a vote of the committee.