He said the state should stop purchasing land if it couldn't pay a reasonable tax rate to local governments to maintain and service it.
"This proposed tax cap is discriminatory," he said, noting the taxpayers of rural municipalities were alone shouldering the burden to make up for the state budget shortfall.
He said the tax cap would cost Warren County taxpayers $300,000 in 2009 in school taxes, and $200,000 to the county government.
Acquario said his organization would help the counties launch a lawsuit challenging the cap if it is enacted.
"We will sue, we will litigate this issue in the courts if the governor and legislators don't reverse this proposal," he said.