Independence Institute director Jon Caldara, who is threatening to sue to stop a property tax increase, on Thursday demanded school districts and counties release information that could help his case.

"There definitely will be a lawsuit," Caldara said.

Denver attorney Richard Westfall will represent him.

Gov. Bill Ritter's spokesman, Evan Dreyer, said the governor is "extremely confident" he would prevail in a lawsuit.

A bill approved by the legislature last spring at Ritter's urging freezes property tax rates in most school districts. The rates would otherwise decline under a 1994 school finance law, reducing the amount property owners pay in taxes.

Caldara claims Colorado's Taxpayer's Bill of Rights requires that Ritter's plan be approved by voters. TABOR requires a vote on any tax policy change that raises more revenue for the state or a district.

Ritter counters that voters in 175 of 178 school districts waived such votes on the school portion of their property taxes in separate referendums over the years.

Caldara is seeking the specific wording of the referendums submitted to voters in each school district.

Caldara believes voters were asked only to allow school districts to keep money they realized in excess of spending caps, not to let tax rates rise and generate more money.