A group of property owners has sued Oakland over the City Council’s certification of a tax measure that failed to reach a standard two-thirds threshold at the polls in November.

City officials were expecting the litigation when they certified Measure AA in December. Taxes in California that go toward specific programs have typically required a supermajority to pass, but proponents of the measure say a recent legal opinion supports their argument that a simple majority was sufficient.

Once collected, the tax revenue would support early childhood education and college readiness programs. The city would tax single-family homes at a rate of $198 a year and multiunit residences at $135 per unit. The measure, championed by Mayor Libby Schaaf, was expected to generate $30 million in annual revenue and last for 30 years.

The City Council certified the measure, 6-1, despite only 62 percent of voters approving it. Councilwoman Lynette Gibson McElhaney voted against certification.

“The city of Oakland has expressed its intention to levy and collect the tax proposed by Measure AA, even though the tax failed to receive the requisite two-thirds vote, and even though official ballot materials, distributed to the voters at taxpayer expense, expressly informed the electorate that a two-thirds vote was required for the measure to take effect,” the lawsuit said.

A spokesman for the city attorney’s office declined to comment because the city had not yet been served or reviewed the complaint.

The lawsuit was filed Friday in Alameda County Superior Court by half a dozen homeowners and landlords as well as the Jobs and Housing Coalition, a group that lobbies City Hall on behalf of businesses and developers.

The coalition, headed by Greg McConnell, had not taken a position on the measure before the election.

“Regardless of the merits of the measure — and who doesn’t like children — the council’s vote, ignoring the will of the voters, is a stunning rebuke to the democratic process, and represents a huge breach of trust to businesses, residents and taxpayers,” McConnell said in a statement.

The suit asks for a court order that would bar the city from collecting the tax.

The League of Women Voters of Oakland also asked the City Council to nullify its earlier action on the tax measure, saying officials had “in effect changed the rules after the game had been played.”

Oakland was following the example set by San Francisco, whose city attorney said in a memo that citizen-initiated tax measures need only a simple majority to pass, based on his interpretation of a recent California Supreme Court decision.

In a statement after the vote explaining her opposition, McElhaney said it would have been better to return to the voters in 2019 or 2020 with a revised measure that could garner more support.

She said the council’s passage would be a blow to public trust and might hurt future efforts to fund essential public services.

“I am concerned that even if the council’s action survives the scrutiny of the court, we may not withstand the ire of our voters,” she said. “Public trust is fragile and must be handled with care.”

Kimberly Veklerov is a San Francisco Chronicle staff writer. Email: kveklerov@sfchronicle.com Twitter: @kveklerov