A Japanese court has declared the results of December’s parliamentary elections invalid and ordered a revote in a district in western Japan, as judges step up pressure on the government over long-delayed electoral reforms.

The ruling in Okayama prefecture Tuesday was one of more than a dozen on “one person, one vote” cases brought by constitutional activists around the country.

It follows a similar ruling Monday, in which a judge in Hiroshima became the first to declare a parliamentary election invalid on constitutional grounds. Unlike the judge in Okayama, however, she did not order a revote, but instead gave the government seven months to address the activists’ complaint: that an unfair distribution of parliamentary seats gives voters in rural areas too much power.

“The distortion caused by this disparity is so heavy that it can no longer be tolerated under the constitution,” the judge, Junko Ikadatsu, said in her ruling.

Japan’s election commission is almost certain to appeal against the Hiroshima and Okayama decisions, meaning that in practice no politician is likely to face sudden unemployment. The national election result — a victory for Prime Minister Shinzo Abe and his Liberal Democratic Party — is also highly unlikely to be affected, experts say.

Even so, the rulings are expected to accelerate changes to an electoral system that legal experts and urban-focused political parties have challenged since at least the 1960s, when Japan’s rapid, industrially driven economic growth drew huge numbers of workers from the countryside to cities.

Redistribution of parliamentary seats did not keep pace with the social shift. By the December general election, each ballot cast by a voter in the most overrepresented rural district, in southwestern Kochi prefecture, was worth 2.43 votes in the most underrepresented one, in Chiba, a suburb of Tokyo.

That such large disparities violate the constitution’s guarantee of voter equality is widely acknowledged. In 2011, the Supreme Court ruled that the previous general election, in 2009, had been conducted “in a state of unconstitutionality.” However, it stopped short of invalidating the results, opting instead to give parliament a chance to fix the system.

Since then, politicians have been deadlocked over proposals to reduce the number of seats in rural areas. Abe’s LDP is seen as especially reluctant to address the issue, because the conservative party has traditionally enjoyed strong support in the countryside.

On Tuesday, the LDP was offering to reduce the number of lower-house parliamentary seats chosen through regional party lists by 30, to 150, with the cuts presumably falling on lower-population areas. But a coalition of five opposition parties rejected the number as too small, as it would represent just 6 percent of all seats in the chamber.

Elections for the legislature’s less powerful upper house are planned for the summer. Yoshimi Watanabe, the leader of Your Party, a group that favors free markets and deregulation and draws much of its support from urban professionals, said Abe should dissolve both houses and call a double election under a new distribution of seats.

“We need to conduct a debate on the right election system quickly and hold a do-over vote,” he said.

Abe is not expected to accede to such demands. After the Hiroshima decision Monday, he said: “I will examine the details and respond appropriately.”

Other court rulings in the recent series of cases followed the Supreme Court’s softer line. In all 14 decisions handed down by regional high courts or their branches, judges confirmed that the December elections violated the constitution, but only those in Hiroshima and Okayama accepted petitioners’ demands to nullify the results in their constituencies.

— Financial Times