Austin is being sued over wording for a petition-driven referendum on the city's $1.2 billion expansion of the convention center and its use of hotel tax revenue.

The head of the local chapter of the NAACP, Nelson Linder, is asking the Texas Supreme Court to force the Austin City Council to rewrite the language that will appear on the November ballot.

The proposition will ask if voters should be required to approve any convention center expansion costing more than $20 million over a four-year period. The city's proposal to expand the center was unanimously passed by the Austin City Council in May. A political action committee drafted a petition challenging that expansion soon after. That petition received more than 20,000 signatures, allowing it to go to a public vote after Council OK'd the ballot language.

The ballot language says the city "must" pay for those elections, but Linder’s attorney, Fred Lewis, argues there would be no cost extra if they were held on even-numbered years at the same time as city council elections.

The petition would also limit the amount of tax revenue from hotel stays that the city puts toward the convention center.

"Yet there’s no reference [in the ballot language] to the fact that it would redirect funds to the arts, historic preservation and other types of tourism," Lewis said.

Lewis, who partly funded the campaign behind the petition-driven referendum, says the city's use of "must" in the language as it refers to the costs of the election is prejudicial and could sway voters.

In a statement, the City of Austin said the council "tried its best to craft ballot language that highlights the chief features of the petitioned ordinance." The city said it will spend the "necessary time, effort, and funds required to respond to the lawsuit."

Meanwhile, the city is forging ahead with its plan to expand the convention center and redevelop the surrounding area, including the historic Palm School. It hopes to nail down its financing of the plan by December and begin construction some time next year.