DENVER (KDVR) — Colorado is facing a legal challenge over a last-minute legislative effort to provide property tax relief.

Proposition HH is set to go before voters this November. The measure aims to lower property tax rates for the next 10 years. To cover resulting revenue losses for local governments, it would also allow the state to use surplus money that would otherwise be refunded because of TABOR.

Advance Colorado, a conservative group, is behind the lawsuit. The group argues that the bill addresses too many topics, in violation of the Colorado Constitution.

“On top of that, the ballot language is unclear and misleading,” Michael Fields, Advance Colorado president, said in a statement. “Voters deserve to know that they would be giving up their TABOR tax refunds in exchange for very little property tax relief.”

Fields, who is also a Republican political analyst for FOX31, also said: “The governor should call a special session to address the property tax crisis without taking away our TABOR refund checks.”

The Taxpayer Bill of Rights caps how much revenue the government can take in and refunds the surplus to Colorado taxpayers. If approved, Proposition HH would kick a separate bill into gear: TABOR refund amounts would be flattened across the board, with each taxpayer to get a $661 check next year.

Gov. Jared Polis has not yet signed either bill, legislative records show.

The lawsuit names the state of Colorado as a defendant, by way of Polis and Secretary of State Jena Griswold.

Property taxpayers in Colorado are facing double-digit increases in their home valuations — and rising property taxes because of that. Colorado Democrats rushed the property tax measure in the waning days of the legislative session, causing contention with Republicans who opposed it.