An unprecedented referendum campaign on the future of the city of Osaka kicked off Monday with appeals from Mayor Toru Hashimoto’s Osaka Ishin no Kai (One Osaka) and from the major established political parties, which all oppose him.

On May 17, the city’s roughly 2.15 million voters will decide whether they want to abolish the 24-ward system and merge them into five semi-autonomous wards with populations between 340,000 and 690,000, by 2017. The move would dissolve the municipal assembly and allow residents in the new wards to elect their own leaders and legislative bodies.

Hashimoto and Osaka Ishin say the consolidation is necessary to streamline the bureaucracy and eliminate redundant services with Osaka Prefecture. That, they say, will improve the local economy and make Osaka’s government more democratic, attracting investment and allowing it to better compete with Tokyo.

“We want Osaka voters to have courage and open up a new door in the city’s history. We can’t eliminate redundancy if we can’t change the system of government,” Osaka Gov. Ichiro Matsui said Monday morning.

But local chapters of the Liberal Democratic Party, Komeito, the Japanese Communist Party and the Democratic Party of Japan oppose the merger, warning it will increase the local tax burden and decrease services at a time when the population is rapidly graying and needs more social welfare services.

They also worry the merger will increase income and social disparities between the city’s generally more prosperous north and predominantly working-class areas in the south.

“If you look at the merger plan carefully, you see there’s nothing but negative consequences. This is the last chance to stop the plan,” said LDP Assemblyman Akira Yanagimoto, also on Monday.

At the moment, Hashimoto and his party are on the defensive. On Sunday, Osaka Ishin lost three mayoral races in the prefecture, including contests in Suita, Yao, and Neyagawa, to LDP-backed candidates, suggesting residents in the area may be turning against the merger. That follows the Osaka municipal and prefectural assembly elections on April 12, in which Osaka Ishin failed to capture a majority.

But with the campaign now underway and few restrictions on getting the message out, both sides expect a fierce public relations battle in the days ahead, especially since interest in the referendum is high. Media polls last month suggested turnout could top 80 percent.