SEATTLE — A coalition of local governments and public transit agencies has begun a legal fight to prevent the voter-approved $30 car-tab measure from taking effect.

Initiative 976, which lowers the vehicle-license fee and targets additional vehicle fees collected by Sound Transit, is a “poorly drafted hodge-podge that violates multiple provisions of the Constitution,” according to a lawsuit filed Wednesday in King County Superior Court.

The suit claims the ballot measure violates the single-subject rule for initiatives, a tenet aimed at ensuring they each address no more than one subject.

The lawsuit also alleges the measure unlawfully impairs existing contracts, referring to bonds sold by Sound Transit that are backed by motor vehicle excise tax collections. And it challenges the legality of the initiative’s elimination of an electric vehicle fee and erasure of local governments’ ability to collect fees through transportation benefit districts.

“The end result of this unconstitutional initiative, I-976, is to decimate revenue and funding for crucial local projects, particularly those related to transportation and transit,” the suit asserts.

The ballot measure is passing with 53% of the vote statewide. It enjoys support in 33 of the state’s 39 counties, including 58.3% who voted yes in Snohomish County.

Tim Eyman, the initiative sponsor and a former Mukilteo resident, issued a statement Wednesday blasting the legal action.

“Rather than accept the voters’ clear decision, Seattle government is suing the voters because the voters disobeyed and voted for it anyway,” he said. “It’s a slap in the face to the people who clearly oppose these dishonest vehicle taxes.”

Opponents say they will seek an injunction in coming days to keep the measure from taking effect on Dec. 5.

Among the plaintiffs are the Association of Washington Cities, and the Washington State Transit Association, whose members include Sound Transit, Community Transit in Snohomish County and Everett Transit. The plaintiffs also include the city of Seattle, King County, the Port of Seattle, Intercity Transit in Thurston County and the Garfield County Transportation Authority.

Attorneys for Seattle, King County and the Pacifica Law Group are handling the litigation on behalf of the other plaintiffs.

Under the state constitution, the initiative will be defended by the Office of the Attorney General.

Jerry Cornfield: 360-352-8623; jcornfield@heraldnet.com. Twitter: @dospueblos.