The House of Lords was formerly composed of the hereditary peers of the realm, life peers, Scottish peers, all peeresses in their own right, and 26 Anglican prelates. In 1999 both houses voted to strip most hereditary peers and peeresses of their right to a seat in the House of Lords; 92 of them remained, some by virtue of offices they hold from the monarch or were elected to by the House, the rest (75) as a result of their election to the body by the hereditary peers. The vast majority of the House consists of life peers proposed by the prime minister and created by the monarch; the titles of life peers cannot be inherited. The membership of the body is not fixed. Formerly headed by the lord chancellor, Lords is now presided over by a lord speaker, a post that was created (2006) when the lord chancellor's duties were reorganized.
Commons is a democratically elected body, currently composed of 650 members: 533 from England, 40 from Wales, 59 from Scotland, and 18 from Northern Ireland. The membership is elected from single-member constinuencies that are periodically redrawn and increased or decreased. The speaker, a generally nonpartisan presiding officer, is elected by members of the party in power. The prime minister must, by modern tradition, be a member of Commons; all other ministers of the cabinet may be from either house.
Although two parties have tended to predominate, a third party has often been important, yet coalition governments have occurred only rarely. The party or coalition controlling a majority chooses the prime minister—the executive head of government—while the largest minority party not in the government functions in Parliament as "Her Majesty's loyal opposition." When the government party is unable to obtain a parliamentary majority on important issues, it is obliged to call a general election for a new Parliament. Elections must be called every five years at the latest, but the government may call an election earlier, at a time of its choosing.
Unlike in the U.S. system, there is no clear separation of legislative and executive branches of the government; the executive branch is, structurally, a committee of the legislature, but because of party discipline, the cabinet, as leadership of the majority party, controls Parliament, while being answerable to it. The British Parliament has had great influence as a model for legislative bodies in other democratic countries.