The Osaka Municipal Assembly on Monday voted down Mayor Toru Hashimoto’s plans to integrate the city into a series of semi-autonomous zones.

Following the vote, which saw only Hashimoto’s Osaka Ishin no Kai (One Osaka) party supporting the bill, the mayor vowed to reintroduce it again next year. He also indicated he may introduce a separate bill to hold a referendum on the issue.

But with an election looming in April, and the fact that any referendum would first require approval from the assembly, which remains opposed to the integration plan, Monday’s rejection represents a major setback for Hashimoto’s efforts to fundamentally restructure Osaka and could spell trouble for his party at the polls.

The vote was not unexpected, as local Liberal Democratic Party and Komeito representatives, along with all opposition parties, have long opposed the mayor’s plan to reorganize Osaka, due to concerns it will cost more than it will save and that administrative services will become less — rather than more — efficient.

There are also concerns among assembly members that Hashimoto’s plan would alter electoral districts and weaken the established parties.

While Osaka Ishin is the largest party in the municipal assembly, the LDP and Komeito control the majority of votes. Officially, the LDP is an opposition party while Komeito works with Osaka Ishin on many other issues.

But relations between Hashimoto and Komeito have worsened in recent months due to differences over the integration plan, which would turn Osaka’s 24 wards into five mini-cities.

Speaking to reporters after the vote, Hashimoto called on residents to start a campaign for a referendum on the issue, and to think about who they want to vote for in April’s local election.

“It’s ridiculous that opposition parties supported by only about 32 percent of voters (in the previous municipal assembly election) have the final decision on this matter,” Hashimoto said.