Reform of the House of Lords is on the agenda again. Here is a timeline explaining the history of Parliament's upper house.
Commons leader Jack Straw outlines proposals for a mixture of elected and appointed peers. MPs back two separate plans - one for a fully elected second chamber and another for one which is 80% elected.
Seven options for reform, from a fully elected to a fully appointed second chamber, were put forward but MPs and peers failed to agree on any of them.
All but 92 hereditary peers are banished from the Lords in what was meant to be the first stage of reform by Labour. Seven years later, the government says it wants to complete those changes.
Women inheriting peerages were allowed to sit and vote in the Lords. And people were allowed to renounce their hereditary peerages - a law sparked by calls by Tony Benn, who had become Viscount Stansgate when his father died.
The Life Peerages Act allowed people of either sex to be made life peers. Allowances for peers' expenses were introduced.
The Parliament Act of 1949 limited the Lords delaying powers to one year - with MPs only having to pass a bill in two successive sessions.
Crisis over the House of Lords erupted when peers rejected the Liberal government's budget in 1909. The Liberals hit back with laws to strip the Lords of power to reject legislation approved by MPs. The Parliament Act of 1911 said "money" bills became law within a month if peers did not pass them without change. And MPs could force through other bills if the Commons passed them in three successive sessions after a two-year delay.
The number of bishops in the Lords was limited in the late 19th century and most Irish and Welsh bishops in any case stopped sitting in the chamber when their churches broke links with the state. In 1876 the first life peers were effectively created when the sovereign was allowed to appoint law lords.
Scottish and Irish peers were allowed to elect some of their number to sit in the Lords after the Acts of Union with Scotland (1707) and Ireland (1800).
The bishops were kept out of the Lords during the Civil War but returned in 1661. The Lords itself ceased to exist from 1649 to 1660. In the 1670s the Commons was officially given the final say on financial matters after attempts by peers to break the convention. And in 1689 the Commons put forward the Bill of Rights, which gave Parliament authority over the king.
Abbots and priors sat in the Lords until 1539 but the dissolution of monasteries saw them removed, leaving only the bishops as the spiritual side of the chamber.
Two distinct Houses of Parliament emerge - the Commons, composed of shire and borough representatives, and the Upper House of religious leaders (lords spiritual) and magnates (lords temporal).
Parliament's origins can be traced to the witans: councils of chief advisers, magnates and religious leaders consulted by Saxon kings.