Unicameral legislatures exist when there is no widely perceived need for multicameralism. Many multicameral legislatures were created to give separate voices to different sectors of society. Multiple chambers allowed for guaranteed representation of different social classes (as in the Parliament of the United Kingdom or the French States-General), ethnic or regional interests, or subunits of a federation. Where these factors are unimportant, in unitary states with limited regional autonomy, unicameralism often prevails. Sometimes, as in New Zealand and Denmark, this comes about through the abolition of one of the two chambers, or, as in Sweden, through the merger of the two chambers into a single one, while in others a second chamber has never existed.
Unicameral legislatures are also common in official Communist states such as the People's Republic of China and Cuba. Similarly, many formerly Communist states, such as Ukraine, Moldova and Serbia, have retained their unicameral legislatures, though others, such as Romania and Poland, adopted bicameral legislatures. Both the former Russian SFSR and the Union of Soviet Socialist Republics (USSR) were bicameral. The two chambers were the Soviet of Nationalities and the Soviet of the Union. The Russian Federation retained bicameralism after the dissolution of the USSR and the transition from existing socialism to capitalism.
The principal advantage of a unicameral system is more efficient lawmaking, as the legislative process is much simpler and there is no possibility of deadlock. Proponents of unicameralism have also argued that it reduces costs, even if the number of legislators stay the same, since there are fewer institutions to maintain and support it.
The main weakness of a unicameral system can be seen as the lack of restraint on the majority, particularly noticeable in parliamentary systems where the leaders of the parliamentary majority also dominate the executive. There is also the risk that important sectors of society may not be adequately represented.
List of unicameral legislatures
Many subnational entities have unicameral legislatures. These include the state of Nebraska and territories of Guam and the Virgin Islands in the United States, the Chinese special administrative regions of Hong Kong and Macau, the Australian state of Queensland as well as the Northern Territory and the Australian Capital Territory, a majority of the provinces of Argentina, all of the provinces and territories in Canada, all of the German states, all of the regions of Italy, all of the Spanish autonomous communities, both the autonomous regions of Portugal, most of the states and union territories of India and all of the states of Brazil. In the United Kingdom, the devolved Scottish Parliament, National Assembly for Wales, London Assembly, and Northern Ireland Assembly are also unicameral.
National Assembly of Angola
National Assembly of Armenia
National Assembly of Azerbaijan
Jatiyo Sangshad of Bangladesh
National Assembly of Benin
National Assembly of Botswana
Legislative Council of Brunei
National Assembly of Bulgaria
National Assembly of Burkina Faso
National Assembly of Cape Verde
National Assembly of the Central African Republic
National Assembly of Chad
Assembly of the Union of the Comoros
Parliament of the Cook Islands
Legislative Assembly of Costa Rica
Sabor of Croatia
Folketing of Denmark
House of Assembly of Dominica
National Assembly of Djibouti
National Parliament of East Timor
National Assembly of Ecuador
House of Representatives of Egypt
Legislative Assembly of El Salvador
National Assembly of Eritrea
Riigikogu of Estonia
Parliament of Fiji
Parliament of Finland
National Assembly of the Gambia
Parliament of Georgia
Parliament of Ghana
Parliament of Greece
Congress of Guatemala
National Assembly of Guinea
National People's Assembly of Guinea-Bissau
National Assembly of Guyana
National Congress of Honduras
National Assembly of Hungary
Althing of Iceland
Islamic Consultative Assembly of Iran
Council of Representatives of Iraq (provision exists for the founding of a "Council of Union", but no move to this effect has been initiated by the existing Council)
Knesset of Israel
House of Assembly of Kiribati
Assembly of Kosovo
Supreme Council of Kyrgyzstan
National Assembly of Kuwait
National Assembly of Laos
Saeima of Latvia
Parliament of Lebanon
House of Representatives of Libya
Landtag of Liechtenstein
Seimas of Lithuania
Chamber of Deputies of Luxembourg
National Assembly of Malawi
Majlis of the Maldives
National Assembly of Mali
Parliament of Malta
Legislature of the Marshall Islands
Parliament of Mauritania
National Assembly of Mauritius
Congress of Micronesia
Parliament of Moldova
National Council of Monaco
State Great Khural of Mongolia
Parliament of Montenegro
Assembly of the Republic of Mozambique
Parliament of Nauru
Parliament of New Zealand
National Assembly of Nicaragua
National Assembly of Niger
Assembly of Niue
Supreme People's Assembly of North Korea
Assembly of North Macedonia
Storting of Norway
National Assembly of Panama
National Parliament of Papua New Guinea
Congress of the Republic of Peru
Assembly of the Republic of Portugal
National Assembly of Saint Kitts and Nevis
Legislative Assembly of Samoa
National Assembly of São Tomé and Príncipe
National Assembly of Senegal
National Assembly of Serbia
National Assembly of Seychelles
Parliament of Sierra Leone
Parliament of Singapore
National Council of Slovakia
National Assembly of South Korea
Parliament of Sri Lanka
National Assembly of Suriname
Riksdag of Sweden
Parliament of Syria
Legislative Yuan of the Republic of China (Taiwan)
National Assembly of Tanzania
National Assembly of Togo
Legislative Assembly of Tonga
National Assembly of Tunisia
Grand National Assembly of Turkey
Assembly of Turkmenistan
Parliament of Tuvalu
Parliament of Uganda
Verkhovna Rada of Ukraine
Pontifical Commission for Vatican City State
National Assembly of Venezuela
National Assembly of Vietnam
Assembly of Representatives of Yemen
National Assembly of Zambia
House of Assembly of the British Virgin Islands
Legislative Assembly of the Cayman Islands
Parliament of Greenland
Parliament of Gibraltar
Legislature of Guam
Legislative Council of Hong Kong
Legislative Assembly of Macau
Legislative Assembly of the Falkland Islands
Legislature of the U.S. Virgin Islands
All legislatures and legislative councils of the regions and communities of Belgium
All legislative assemblies of the provinces and territories of Canada
All legislative assemblies of the states of Malaysia
Parliament of Queensland and the legislative assemblies of the territories of Australia (but not the other states)
Provincial legislatures of the provinces of South Africa
Narodna skupština of Republika Srpska
All legislative assemblies in all states of Brazil
All legislatures in all states of Mexico
15 of the provinces of Argentina – Chaco, Chubut, Córdoba, Formosa, Jujuy, La Pampa, La Rioja (Argentina), Misiones, Neuquén, Río Negro (Argentina), San Juan, Santa Cruz, Santiago del Estero, Tierra del Fuego, Tucumán and the autonomous city of Buenos Aires.
22 of the states of India – Arunachal Pradesh, Assam, Chhattisgarh, Goa, Gujarat, Haryana, Himachal Pradesh, Jharkhand, Kerala, Madhya Pradesh, Manipur, Meghalaya, Mizoram, Nagaland, Odisha, Punjab, Rajasthan, Sikkim, Tamil Nadu, Tripura, Uttarakhand and West Bengal; and 2 of the union territories – Delhi and Puducherry
All legislatures of the provinces in Pakistan – Azad Kashmir, Balochistan, Gilgit Baltistan Khyber Pakhtunkhwa, Punjab and Sindh
Iraqi Kurdistan Parliament
Northern Ireland Assembly
[[INLINE_IMAGE|//upload.wikimedia.org/wikipedia/commons/thumb/1/10/Flag_of_Scotland.svg/23px-Flag_of_Scotland.svg.png|//upload.wikimedia.org/wikipedia/commons/thumb/1/10/Flag_of_Scotland.svg/35px-Flag_of_Scotland.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/10/Flag_of_Scotland.svg/46px-Flag_of_Scotland.svg.png 2x|Scotland|h14|w23|thumbborder flagicon-img flagicon-img]] Scottish Parliament
National Assembly for Wales
Parliaments of the autonomous communities of Spain
All regional councils of France
Local People's Congresses of all levels of provinces, regions and municipalities of the People's Republic of China
List of historical unicameral legislatures
The First Protectorate Parliament and Second Protectorate Parliament of the Kingdom of England, regulated by the Instrument of Government (dissolved)
Parliament of the Kingdom of Scotland until 1707 (dissolved)
Congress of the Confederation was unicameral before being replaced in 1789 by the current, bicameral United States Congress.
Congress of Deputies of Second Spanish Republic was unicameral between 1931 and 1936. Dissolved at the end of Spanish Civil War; the present Spanish Parliament (established in 1978) is bicameral.
Supreme Assembly of Uzbekistan was unicameral before being replaced in 2005 by the current, bicameral Supreme Assembly.
National Assembly of Cameroon was unicameral before being replaced in 2013 by the current, bicameral Parliament of Cameroon.
Chamber of People's Representative of Equatorial Guinea was unicameral before being replaced in 2013 by the current, bicameral Parliament of Equatorial Guinea.
National Assembly of Kenya was the country's unicameral legislature before becoming the lower house of the bicameral Parliament of Kenya in 2013.
National Assembly of Ivory Coast was the country's unicameral legislature before becoming the lower house of the bicameral Parliament of Ivory Coast in 2016.
Unicameralism in the United States
Within U.S. states, Nebraska is currently the only state with a unicameral legislature; after a statewide vote, it changed from bicameral to unicameral in 1937. A 2018 study found that efforts to adopt unicameralism in Ohio and Missouri failed due to rural opposition. There was a fear in rural communities that unicameralism would diminish their influence in state government.
Local government legislatures of counties, cities, or other political subdivisions within states are usually unicameral and have limited lawmaking powers compared to their state and federal counterparts.
In 1999, Governor Jesse Ventura proposed converting the Minnesota Legislature into a single unicameral chamber. Although debated, the idea was never adopted.
The U.S. territory of Puerto Rico held a non-binding referendum in 2005. Voters approved changing its Legislative Assembly to a unicameral body by 456,267 votes in favor (83.7%) versus 88,720 against (16.3%). If both the territory's House of Representatives and Senate had approved by a 2⁄3 vote the specific amendments to the Puerto Rico Constitution that are required for the change to a unicameral legislature, another referendum would have been held in the territory to approve such amendments. If those constitutional changes had been approved, Puerto Rico could have switched to a unicameral legislature as early as 2015.
On June 9, 2009, the Maine House of Representatives voted to form a unicameral legislature, but the measure did not pass the Senate.
Because of legislative gridlock in 2009, former Congressman Rick Lazio, a prospective candidate for governor, has proposed that New York adopt unicameralism.
Unicameralism in the Philippines
Though the current Congress of the Philippines is bicameral, the country experienced unicameralism in 1898 and 1899 (during the First Philippine Republic), from 1935 to 1941 ( the Commonwealth era) and from 1943 to 1944 (during the Japanese occupation). Under the 1973 Constitution, the legislative body was called Batasang Pambansa, which functioned also a unicameral legislature within a semi-presidential system form of government until 1986.
The ongoing process of amending or revising the current Constitution and form of government is popularly known as Charter Change. A shift to a unicameral parliament was included in the proposals of the constitutional commission created by former President Gloria Macapagal-Arroyo. Unlike in the United States, senators in the Senate of the Philippines are elected not per district and state but nationally; the Philippines is a unitary state. The Philippine government's decision-making process, relative to the United States, is more rigid, highly centralised, much slower and susceptible to political gridlock. As a result, the trend for unicameralism as well as other political system reforms are more contentious in the Philippines.
While Congress is bicameral, all local legislatures are unicameral: the ARMM Regional Legislative Assembly, the Sangguniang Panlalawigan (Provincial Boards), Sangguniang Panlungsod (City Councils), Sangguniang Bayan (Municipal Councils), Sangguniang Barangay (Barangay Councils) and the Sangguniang Kabataan (Youth Councils).