Unicameralism (from uni- "one" + Latin camera "chamber") is a type of legislature, which consists of one house or assembly, that legislates and votes as one.[1] Unicameralism has become an increasingly common type of legislature, making up nearly 60% of all national legislatures[2] and an even greater share of subnational legislatures.

Sometimes, as in New Zealand and Denmark, unicameralism comes about through the abolition of one of two bicameral 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 from the beginning.

Rationale for unicameralism and criticism

The principal advantage of a unicameral system is more efficient lawmaking, as the legislative process is simpler and there is no possibility of deadlock between two chambers. Proponents of unicameralism have also argued that it reduces costs, even if the number of legislators stays the same, since there are fewer institutions to maintain and support financially. More popular among modern-day democratic countries, unicameral, proportional legislatures are widely seen as both more democratic and effective.[3]

Proponents of bicameral legislatures say that having two legislative chambers offers an additional restraint on the majority, though critics note that there are other ways to restrain majorities, such as through non-partisan courts and a robust constitution.[4]

List of unicameral legislatures

  Countries with a bicameral legislature.
  Countries with a unicameral legislature.
  Countries with a unicameral legislature and an advisory body.
  Countries with no legislature.

Approximately half of the world's sovereign states are currently unicameral. The People's Republic of China is somewhat in-between, with a legislature and a formal advisory body. China has a Chinese People's Political Consultative Conference which meets alongside the National People's Congress, in many respects an advisory "upper house".

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 Macao, 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, the Senedd Cymru, the Northern Ireland Assembly, and the London Assembly are also unicameral.


North America
South America


State parliaments with limited recognition


Provincial legislatures in Argentina

Devolved governments


List of historical unicameral legislatures




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 parliamentary system (1973-1981) and a semi-presidential system (1981-1986) form of government.

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 President Gloria Macapagal Arroyo.[7] 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.[8] 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.[9]

While Congress is bicameral, all local legislatures are unicameral: the Bangsamoro Parliament, the Sangguniang Panlalawigan (Provincial Boards), Sangguniang Panlungsod (City Councils), Sangguniang Bayan (Municipal Councils), Sangguniang Barangay (Barangay Councils), and the Sangguniang Kabataan (Youth Councils).

Unicameralism in the United States

The Nebraska Legislature (also called the Unicameral) is the supreme legislative body of the state of Nebraska and the only unicameral state legislature in the United States. Its members are called "senators", as it was originally the upper house of a bicameral legislature before the Nebraska House of Representatives dissolved in 1937. The legislature is also notable for being nonpartisan and officially recognizes no party affiliation, making Nebraska unique among U.S. states. With 49 members, it is also the smallest legislature of any U.S. state.

A 2018 study found that efforts to adopt unicameralism in Ohio and Missouri failed due to rural opposition.[10] There was a fear in rural communities that unicameralism would diminish their influence in state government.[10]

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.

Some of the 13 colonies which became independent, such as Pennsylvania, New Jersey and New Hampshire had initially introduced strong unicameral legislature and (relatively) less powerful governors with no veto power. Pennsylvania's constitution lasted only 14 years. In 1790, conservatives gained power in the state legislature, called a new constitutional convention, and rewrote the constitution. The new constitution substantially reduced universal male suffrage, gave the governor veto power and patronage appointment authority, and added an upper house with substantial wealth qualifications to the unicameral legislature. Thomas Paine called it a constitution unworthy of America.

In 1999, Governor Jesse Ventura proposed converting the Minnesota Legislature into a single chamber.[11] Although debated, the idea was never adopted.

Seven U.S. states, Arizona, Idaho, Maryland, New Jersey, North Dakota, South Dakota, and Washington, effectively have two-house unicamerals. In these states, districts in the upper house and the lower house are combined into a single constituency, a practice known as nesting.

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%).[12] If both the territory's House of Representatives and Senate had approved by a 23 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.[13]

Because of legislative gridlock in 2009, former Congressman Rick Lazio, a prospective candidate for governor, has proposed that New York adopt unicameralism.[14]

The United States as a whole was subject to a unicameral Congress during the years 1781–1788, when the Articles of Confederation were in effect. The Confederate States of America, pursuant to its Provisional Constitution, in effect from February 8, 1861, to February 22, 1862, was governed by a unicameral Congress.[15]


  1. The Bundestag is technically the unicameral parliament of Germany, since the Bundesrat is not defined as a chamber of the legislature, but a completely separate legislative institution according to the Basic Law (German constitution).
  2. Geographically a part of Asia but geopolitically a part of Europe.
  3. Transcontinental country.
  4. The original constitution is partially superseded by the additional articles only on Taiwan which replaced the tricameral parliament into a unicameral one. A sunset clause in the additional articles will terminate them in the event of a hypothetical resumption of ROC rule in Mainland China.


  1. Lanham, Url (1918–1999) (2018). The insects. ISBN 978-81-89729-42-4. OCLC 1003201754.
  2. "IPU PARLINE database: Structure of parliaments". archive.ipu.org. 2022. Retrieved 2022-12-31.
  3. Wirls, Daniel (2004). The invention of the United States Senate. Stephen Wirls. Baltimore: Johns Hopkins University Press. ISBN 0-8018-7438-6. OCLC 51878651.
  4. Litt, David (2020). Democracy in one book or less : how it works, why it doesn't, and why fixing it is easier than you think (First ed.). New York, NY. ISBN 0-06-287936-7. OCLC 1120147424.
  5. Reuter, Konrad (2003). "Zweite Kammer?". Bundesrat und Bundesstaat: Der Bundesrat der Bundesrepublik Deutschland(PDF) (in German) (12th ed.). Berlin: Direktor des Bundesrates. p. 50. ISBN 3-923706-22-7. Archived from the original (PDF) on 2007-06-28. Retrieved 2007-01-04. Im Ausland wird ein solches parlamentarisches System im Allgemeinen als Zweikammer- System bezeichnet. Für Bundestag und Bundesrat ist dagegen eine gemeinsame Bezeichnung nicht allgemein üblich, und es ist sogar umstritten, ob der Bundesrat eine Zweite Kammer ist. (English: Abroad, such a parliamentary system is in general called a bicameral one. For Bundestag and Bundesrat such a common designation is not usual and it is even contentious whether the Bundesrat is a second chamber at all.)
  6. Jones, Seth G. (December 2020). "Afghanistan's Future Emirate? The Taliban and the Struggle for Afghanistan". CTC Sentinel. Combating Terrorism Center. 13 (11). Retrieved 2 November 2022.
  7. "Constitutional Commission proposals". Concom.ph. Retrieved 2013-11-26.
  8. Softrigger Interactive (2008-02-25). "Philippines : Gov.Ph : About the Philippines". Archived from the original on February 25, 2008. Retrieved 2013-11-26.
  9. "Why Change?". Concom.ph. Archived from the original on 2006-08-18. Retrieved 2013-11-26.
  10. Myers, Adam S. (2018). "The Failed Diffusion of the Unicameral State Legislature, 1934–1944". Studies in American Political Development. 32 (2): 217–235. doi:10.1017/S0898588X18000135. ISSN 0898-588X. S2CID 150363451.
  11. "One People – One House". News.minnesota.publicradio.org. 1999-04-29. Retrieved 2013-11-26.
  12. "Referéndum sobre el Sistema Cameral". Comisión Estatal de Elecciones de Puerto Rico. 2005-07-10.
  13. "RESOLUTION, Proposing an Amendment to the Constitution of Maine To Establish a Unicameral Legislature" (PDF). Retrieved 2013-11-26.
  14. One for All, Rick Lazio, New York Times, July 14, 2009
  15. "Avalon Project - Confederate States of America - Constitution for the Provisional Government". avalon.law.yale.edu.
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