A parliamentary system, or parliamentarism, is distinguished by the executive branch of government being dependent on the direct or indirect support of the parliament, often expressed through a vote of confidence. Hence, there is no clear-cut separation of powers between the legislative and executive branches of government. Parliamentary systems usually have a clear differentiation between the head of government and the head of state.
The term parliamentary system does not mean that a country is ruled by different parties in coalition with each other. Such multi-party arrangements are usually the product of a voting system known as proportional representation. Parliamentary nations that use first past the post voting usually have governments composed of one party. The United Kingdom, for instance, has not had a coalition government since World War II. However, parliamentary systems of continental Europe do use proportional representation, and it seems that PR voting systems and coalition governments usually go together.
The executive is typically a cabinet, and headed by a prime minister who is considered the head of government, but parliamentarism has also been practised with privy councils and the Senate of Finland. The prime minister and the ministers of the cabinet typically have their background in the parliament and may remain members thereof while serving in cabinet. The leader of the leading party, or group of parties, in the parliament is often appointed as the prime minister.
In many countries, the cabinet, or single members thereof, can be removed by the parliament through a vote of no confidence. In addition, the executive can often dissolve the parliament and call extra-ordinary elections.
Under the parliamentary system the roles of head of state and head of government are more or less separated. In most parliamentary systems, the head of state is primarily a ceremonial position, often a monarch or president, retaining duties that aren't politically divisive, such as appointments of civil service.
In many parliamentary systems, the head of state may have reserve powers which are usable in a crisis. In most cases however, such powers are (either by convention or by constitutional rule) only exercised upon the advice and approval of the head of government.
Parliamentary systems vary as to the degree to which they have a formal written constitution and the degree to which that constitution describes the day to day working of the government. They also vary as to the number of parties within the system and the dynamics between the parties. Also, relations between the central government and local governments vary in parliamentary systems, they may be federal or unitary states. Parliamentary systems also vary in the voting freedom allowed back bench legislators.
Parliamentarism is praised, relative to presidentialism, for its flexibility and responsiveness to the public. It is faulted for its tendency to sometimes lead to unstable governments, as in the German Weimar Republic, the French Fourth Republic, Italy, and Israel.
Criticisms of a parliamentary system of government
Some believe that a parliamentary system can place too much power in the executive branch (often a prime minister and a cabinet in such a system). Others feel that the legislature or judiciary have little scope to administer checks or balances on the executive.
However, some reckon that it's relatively easier to pass legislation within a parliamentary system, since the executive and legislative branches are more dependent on each other than in a system with a completely seperated executive. Within presidential systems, the executive is often chosen independently from the legislature. If the executive is of a different party from those leading the legislature, then stalemate can occur. See cohabitation for a related discussion.
List of countries with a parliamentary system of government