ATHENS—Greece's lawmakers on Thursday passed a radical change to the country's electoral system, which the left-wing government says will make the political system more democratic.

Critics, however, say the law will make the crisis-racked nation even harder to govern and complicate future attempts to form coalition governments.

The new law scraps the 50-seat bonus in parliament that goes to the party with the most votes. Without the bonus, seats in parliament will simply reflect the share of all votes among parties that get more than 3% support.

In Greece's 300-seat legislature, the majority of lawmakers approved the law, but the government was short of the 200 votes needed to bring the new electoral system into force in time for the next elections.

Instead, the new system would take effect after the next elections, due in September 2019, raising the risk that it could be changed or reversed by the next government.

Shortly before the vote took place, Prime Minister Alexis Tsipras told lawmakers that the change marks the start of a new political era for Greece that is needed for the country to exit the economic crisis.

"This change meets society's demand for a rationalization and renewal of the political system," he said.

Greece's electoral system has undergone various changes since democracy was restored in 1974, but the system has generally rewarded the most popular party, usually allowing for one-party governments. Only rarely have coalitions or bipartisan consensus been necessary—one recent coalition example being the current one between the left-wing Syriza party and right-wing Independent Greeks.

In theory, Greece holds elections every four years. In practice, few recent governments have lasted that long. The country held two snap elections in 2015.

The new law also cuts the voting age to 17 from 18, in a popular move on Greece's political left, which has strong support among the country's youth.

Write to Stelios Bouras at stelios.bouras@wsj.com

(END) Dow Jones Newswires

July 21, 2016 21:25 ET (01:25 GMT)