Labor unions continued to be the predominant backer of the main opposition coalition to the constitutional convention referendum that is being put before voters next month.

The group New Yorkers Against Corruption includes a broad swath of organizations — from environmental groups to the New York State Rifle And Pistol Association, as well as labor unions and the Conservative Party.

The main backers of the group continue to be organized labor. A filing with the Board of Elections shows the group has raised $724,696 since the middle of July, with contributions including $100,000 from the Public Employees Federation, $120,000 from the New York Pipe Trades Association and $50,000 from the AFL-CIO.

Anti-convention organizers are concerned that holding an effort to rewrite or change the constitution could lead to a challenge to hard-won benefits and rights in the existing document. Labor would also likely run delegates to a convention, diverting resources in a statewide election year.

Those in favor of the constitutional convention include wealthy Democratic fundraiser Bill Samuels, who has spent thousands of dollars on his own pro-con con effort, as well as the state Bar Association.

The filing by New Yorekrs Against Corruption shows the group has spent its money so far on digital ad purchases, consultants and the retaining of attorney James Long.