A parliamentary system is a system of democratic governance of a state where the executive branch derives its democratic legitimacy from the legislature (parliament) and is also held accountable to that legislature. In a parliamentary system, the head of state is normally a different person from the head of government. This is in contrast to a presidential system, where the head of state often is also the head of government, and most importantly, the executive branch does not derive its democratic legitimacy from the legislature.
Countries with parliamentary systems may be constitutional monarchies, where a monarch is the head of state while the head of government is almost always a member of the legislature (such as the United Kingdom, Denmark, Sweden and Japan), or parliamentary republics, where a mostly ceremonial president is the head of state while the head of government is regularly from the legislature (such as Ireland, Germany, India and Italy). In a few parliamentary republics, such as Botswana, South Africa, Switzerland and Suriname, as well as German states, the head of government is also head of state, but is elected by and is answerable to the legislature.
The first parliaments date back to the Middle Ages, for example in 1188 Alfonso IX, King of Leon convened the three states in the Cortes of León. An early example of parliamentary government developed in today's Netherlands and Belgium during the Dutch revolt (1581), when the sovereign, legislative and executive powers were taken over by the States General of the Netherlands from the then-monarch, King Philip II of Spain. The modern concept of parliamentary government emerged in the Kingdom of Great Britain (1707–1800) and its contemporary, the Parliamentary System in Sweden (1721–1772).
In 1714, Prince Elector George Ludwig of Hanover, Germany, acceded to the throne of Great Britain after his cousin Queen Anne died with no heirs of her body. As King George I he chaired the cabinet and chose ministers of the government; however, he initially spoke no English. This shifted the balance of power towards the leading minister, or first minister, who de facto chaired the cabinet. During his reign, Parliament's role in controlling government and in deciding who the king could ask to form a government gradually increased. Towards the end of his reign, actual power was held by Sir Robert Walpole, who evolved as Britain's first prime minister over the years from 1721 to 1742. Later, the Great Reform Act of 1832 broadened the franchise and was accompanied by increasing parliamentary dominance, with Parliament always deciding who was prime.
A parliamentary system may use bicameralism with two chambers of parliament (or houses): an elected lower house, and an upper house or Senate which may be appointed or elected by a different mechanism from the lower house. Another possibility is unicameralism with just one parliamentary chamber.
Scholars of democracy such as Arend Lijphart distinguish two types of parliamentary democracies: the Westminster and Consensus systems.
Implementations of the parliamentary system can also differ on the manner of how the prime minister and government are appointed and as to whether the government needs the explicit approval of the parliament, rather than just the absence of its disapproval. Some countries such as India also require the prime minister to be a member of the legislature, though in other countries this only exists as a convention.
Furthermore, there are variations as to what conditions exist (if any) for the government to have the right to dissolve the parliament:
The parliamentary system can be contrasted with a presidential system which operates under a stricter separation of powers, whereby the executive does not form part of, nor is appointed by, the parliamentary or legislative body. In such a system, parliaments or congresses do not select or dismiss heads of governments, and governments cannot request an early dissolution as may be the case for parliaments. There also exists the semi-presidential system that draws on both presidential systems and parliamentary systems by combining a powerful president with an executive responsible to parliament, as for example the French Fifth Republic.
A few parliamentary democratic nations such as India, Pakistan, and Bangladesh, have enacted an anti-defection law, which prohibits a member of the legislature from switching to another party after being elected. With this law, elected representatives lose their seats in parliament if they vote contrary to the directions of their party.
Advantages and disadvantages
One of the commonly attributed advantages to parliamentary systems is that it is faster and easier to pass legislation, as the executive branch is formed by the direct or indirect support of the legislative branch and often includes members of the legislature. Thus the executive (as the majority party or coalition of parties in the legislature) has a majority of the votes, and can pass legislation at will. In a presidential system, the executive is often chosen independently from the legislature. If the executive and the majority of the legislature are from different political parties, then stalemate can occur. Thus the executive might not be able to implement its legislative proposals. An executive in any system (be it parliamentary, presidential or semi-presidential) is chiefly voted into office on the basis of his or her party's platform/manifesto, and the same is also true of the legislature.
In addition to quicker legislative action, parliamentary government has attractive features for nations that are ethnically, racially, or ideologically divided. In a presidential system, all executive power is vested in one person: the president. In a parliamentary system, with a collegial executive, power is more divided. In the 1989 Lebanese Taif Agreement, in order to give Muslims greater political power, Lebanon moved from a semi-presidential system with a strong president to a system more structurally similar to classical parliamentary government. Iraq similarly disdained a presidential system out of fears that such a system would be tantamount to Shiite domination; Afghanistan's minorities refused to go along with a presidency as strong as the Pashtuns desired.
It can also be argued that power is more evenly spread out in parliamentary government. The prime minister is seldom as important as a ruling president, and there tends to be a higher focus on voting for a party and its political ideas than voting for an actual person.
In his 1867 book The English Constitution, Walter Bagehot praised parliamentary government for producing serious debates, for allowing change in power without an election, and for allowing elections at any time. Bagehot considered the four-year election rule of the United States to be unnatural.
Some scholars like Juan Linz, Fred Riggs, Bruce Ackerman, and Robert Dahl claim that parliamentary government is less prone to authoritarian collapse. These scholars point out that since World War II, two-thirds of Third World countries establishing parliamentary governments successfully made the transition to democracy. By contrast, no Third World presidential system successfully made the transition to democracy without experiencing coups and other constitutional breakdowns.
A recent World Bank study found that parliamentary systems are associated with less corruption.
Some constituencies may have a popular local candidate under an unpopular leader (or the reverse), forcing a difficult choice on the electorate. Mixed-member proportional representation (where voters cast two ballots) can make this choice easier by allowing voters to cast one vote for the local candidate but also cast a second vote for another party.
Although Bagehot praised parliamentary government for allowing an election to take place at any time, the lack of a definite election calendar can be abused. Previously under some systems, such as the British, a ruling party could schedule elections when it felt that it was likely to retain power, and so avoid elections at times of unpopularity. (Election timing in the UK, however, is now partly fixed under the Fixed-term Parliaments Act 2011.) Thus, by wise timing of elections, in a parliamentary system a party can extend its rule for longer than is feasible in a functioning presidential system. This problem can be alleviated somewhat by setting fixed dates for parliamentary elections, as is the case in several of Australia's state parliaments. In other systems, such as the Dutch and the Belgian, the ruling party or coalition has some flexibility in determining the election date. Conversely, flexibility in the timing of parliamentary elections can avoid periods of legislative gridlock that can occur in a fixed period presidential system.
Critics of the Westminster parliamentary system point out that people with significant popular support in the community are prevented from becoming prime minister if they cannot get elected to parliament since there is no option to "run for prime minister" as one can run for president under a presidential system. Additionally, prime ministers may lose their positions if they lose their seats in parliament, even though they may still be popular nationally. Supporters of parliamentary government respond by saying that as members of parliament, prime ministers are elected first to represent their electoral constituents and if they lose their support then consequently they are no longer entitled to be prime minister.