Following the enactment of the House of Lords Act 1999, the number of hereditary peers entitled to sit in the House of Lords was reduced to ninety-two. The Earl Marshal and the Lord Great Chamberlain were entitled to sit ex officio; the remaining ninety were elected by all the hereditary peers before the passing of the reform. Since November 2002, by-elections have been held to fill vacancies left by deaths, resignations or disqualifications of those peers. Since the passing of the House of Lords Reform Act 2014, by-elections have also been held to fill vacancies left by the retirements of those peers.
Before the passing of the 1999 Act, the Lords approved a Standing Order stating that the remaining hereditary peers shall consist of:
2 peers to be elected by the Labour hereditary peers
42 peers to be elected by the Conservative hereditary peers
3 peers to be elected by the Liberal Democrat hereditary peers
28 peers to be elected by the Crossbench hereditary peers
15 peers to be elected by the whole House
The holders of the offices of Earl Marshal and Lord Great Chamberlain to be ex officio members. The current holder of the office of Lord Great Chamberlain was previously elected to the House of Lords in a by-election. As a result, there are currently 91 seats for excepted hereditary peers in the House of Lords.
Elections must be held within three months of a vacancy occurring, and they take place under the Alternative Vote system. All those on the Register of Hereditary Peers are eligible to stand, but only sitting (the "excepted") hereditary peers may vote for the 75 seats reserved for a single parliamentary group (which can result in very small electorates, such as three voters in the 2003 election of Lord Grantchester); for the 15 peers elected by the whole house, life peers may also vote.
As of September 2023, there have been 18 by-elections among Conservative peers; 19 by-elections among Crossbench peers; 2 among Liberal Democrat peers; and 2 among Labour peers. In addition, there have been 14 by-elections by the whole House.
Current composition
, the party affiliations of the elected hereditary peers are as follows:
One additional hereditary peer is an ex officio member of the Lords: Duke of Norfolk (Earl Marshal).
By-election results
2003
After the death of the Viscount of Oxfuird
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After the death of Lord Milner of Leeds
2004
After the death of Lord Vivian:
2005
After the death of the Earl Russell:
After the death of Lord Burnham:
After the death of Lord Aberdare:
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After the death of Baroness Strange:
2007
After the death of Lord Mowbray and Stourton:
2008
After the death of the Baroness Darcy de Knayth:
2009
After the death of the Viscount Bledisloe:
