At the start of a Parliament the chairs of a number of select committees are elected by the House.
How Chair elections work
Most select committee chairs are elected by the whole House in a secret ballot held after each general election and at other times when a vacancy arises. This briefing note ( PDF 56 KB) provides information about the election process.
The chairs of all the departmental select committees, as well as the chairs of the Environmental Audit, Exiting the European Union, Petitions, Public Administration and Constitutional Affairs, Public Accounts, Procedure, and Standards Committees, are elected in this way. The chairs of Standards and Public Accounts must come from the official Opposition.
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.