Describing an assembly held at Wislica in 1382, 15th century chronicler Jan Dlugosz referred to it as Diet (dieta in Latin). Some historians regard the Wislica assembly as the opening chapter in the history of the Sejm. In the 15th century, the Kingdom of Poland had three kinds of assemblies operating simultaneously, namely the regional assemblies (attended by all noblemen and gentry from the given region), provincial assemblies for Malopolska and Wielkopolska and the national assembly, called the General Sejm, which was composed of the Royal Council, senior officials, noblemen, gentry and representatives of mayor towns and Church chapters.
In 1493, the regional assemblies began sending regularly their representatives to the General Sejm. The year 1493 marks the beginning of the two-house parliament composed of the Senate and the House of Deputies.
A rise in the importance of parliament was confirmed by the 1505 Sejm Act, or constitution, generally referred to as the Nihil Novi Act. It said that "ever since, nothing new designed to change the common law or public freedom shall be determined without joint agreement of senators and regional deputies.
"The Sejm passed laws, imposed taxes, conferred titles, received foreign envoys, laid down foreign policy guidelines, controlled the treasury, approved levy in mass, and had the right to order reprieve and amnesty. Until the 70s of XVI cent., the Sejm met frequently if irregularly in different towns. Following the Union of Lublin (1569), the composition of the General Sejm was extended to include senators and deputies representing the Grand Duchy of Lithuania.
From 1572, the Sejm met at Warsaw's Royal Castle. Its sessions were held for six weeks every two years. There was also a possibility of convening an Extraordinary Sejm.
In 1the late 17th century it was decided that every third Sejm would meet in the Grand Duchy of Lithuania.
In 1573, the Sejm guaranteed religious peace between the various Christian believers and ensured religious dissidents the protection of the state.
Religious tolerance was an important characteristic feature of the Republic of Two Nations. Another important feature was a large proportion of noblemen and gentry (collectively called szlachta) who represented from 8 to 10 per cent of the population. This body politic - people continuously participating in public affairs - was several times stronger in numbers than in other countries. The noblemen and gentry, for instance, had the right of direct participation in convocation and election Sejms at which Poland's kings were elected (viritim elections).
Deriving from absolute equality of all szlachta, the principle of unanimity in decision-making eventually produced the institution of liberum veto. And so from 1652, a single deputy's objection sufficed to prevent Sejm debates from continuing and to invalidate all the previously adopted resolutions. Some decades later, the liberum veto principle practically incapacitated central authority. Its weakening strengthened the importance of regional assemblies, coming under an influence of the magnates who took advantage of this fact to paralyse whatever modest attempts at changing the status quo were made.
Following fragmentary reforms introduced in the 1760s and 1770s, the Four-Year Sejm (1788- 1792) embarked upon the giant task of transforming the state. The 3rd May Constitution adopted by this Sejm in 1791, only the second such constitution in the world after the American one, said that "all power in the community of men derives from the will of the nation". The principle of the nation's sovereignty was accompanied by the adoption of the Montesquieuan division of power. The Constitution assigned to the House of Deputies and the Senate, the position of the supreme organ of state power. It was also the first such act in the world which introduced in the form of statutory provision the principle of the ministers' accountability to parliament. The Four-Year Sejm also reformed the army, the treasury and public administration.
Poland's partitions (1772, 1793, 1975) by Russia, Prussia and Austria prevented these reforms from materialising, however.
From 1795 to 1918, public life in Poland could not develop normally due to the lack of statehood. The activity of regional assemblies in the Duchy of Warsaw and the Congress Kingdom (within the Russian Empire till the fall of the 1830 November Insurrection) or Poles' participation in the legislative institutions of the partitioning powers were but a token of public activity.
Poland regained independence in November 1918. The Constitutional Assembly, the first democratically elected single-house parliament of reborn Poland, held its first sitting as early as February 10, 1919. These were the first elections in Poland in which women had the right to vote (women were enfranchised in Poland earlier than, for instance, in Britain, the United States or France). The Constitution passed by the Assembly on March 17, 1921, ushered in a two-house parliament and granted to the Sejm, composed of 444 deputies, the dominating position over the 111-seat Senate and the executive authorities. Constitutional amendments introduced in the wake of Pilsudski's May coup in August 1926 strengthened the powers of the President and Government and weakened the Sejm's previous position.
From May 1926 a conflict was on between the ruling camp, which wanted to shape a new model of the state, and the parliamentary majority. A new Constitution adopted in April 1935 abandoned the classic separation of powers, reduced the role of thee Sejm, and concentrated authority in the hands of the President.
At the outset of World War II, the Sejm had its last meeting on September 2, 1939. It declared the determination to defend Poland's independence and unanimously passed an act enabling Sejm deputies and senators to join the army.
On September 17, 1939, Poland's state authorities were forced to emigrate.
On December 1 of that year, following the formal dissolution of the Sejm and the Senate, the President announced that elections to both houses of parliament would be held sixty days after the end of the War. The London-based Polish National Council acted as the Sejm in exile.
At the Yalta conference, the Allies agreed that free and unrestricted elections should be held in Poland at the earliest opportunity. But in the system of communist dictatorship which was imposed on Poland after World War II, the Sejms were chosen in undemocratic elections and though they formally enjoyed far-reaching prerogatives, their neither exercised genuine power nor represented the public. Nevertheless, even during those years, the Polish Sejm played a bigger role than its counterparts in other communist countries.
The August 1980 strikes and the founding of Solidarity started a process of deep political and social changes. The 1989 Round Table agreements, led to partly democratic elections of June 4 of that year. As a result of these elections, the 10th Sejm was chosen and the Senate was revived. On December 29, 1989, the Sejm restored the country's historical name of the Republic of Poland and its traditional national emblem, namely the crowned eagle. That Sejm also passed over 200 statutory acts which laid the groundwork for a system of parliamentary democracy and a 3market economy. The 10th Sejm's decision to disband and shorten its term and the passing of a new electoral law on June 28, 1991, made it possible for the President to order the first fully democratic parliamentary elections in postwar Poland.
The Sejm elected on October 27, 1991 worked from November 25, 1991 to May 31, 1993, when it was dissolved by the President. By that time, it passed 95 acts, including the Constitutional Act on the mutual relations between the legislative and executive institutions of the Republic of Poland and on local self-government. Pending the adoption of the new Constitution of the Republic of Poland, the October 17, 1992 act, commonly referred to as "Interim Constitution," determines the relations between the Sejm, the President and the Government. In this system, the Sejm along with the Senate constitute the supreme legislative organs of the state.
A new Sejm and Senate of the Republic of Poland were elected on September 19, 1993. The inaugural sitting of the Sejm was held on October 14 and that of the Senate on October 15, 1993.
The present Marshal of the Sejm is Józef Zych.
On April 2, 1997, the National Assembly passed the Constitutional Act which was accepted in the constitutional referendum on May 25, 1997.