SOMERSET -- Gov. Chris Christie said Wednesday a measure both Republicans and Democrats credit for helping to curb rising property taxes will expire at the end of the year unless Democratic gubernatorial nominee Phil Murphy throws his support behind it before Dec. 31.

Without it, the governor predicted, your property taxes could soar again.

The governor was referring to New Jersey's 2 percent cap on raises for police and firefighters who go to arbitration. Christie said he would sign a bill during a lame-duck session after Election Day, but leaders of the Democratic-controlled Legislature are waiting for Murphy to stake a claim on the issue, he said.

Instead, Murphy, a former U.S. ambassador to Germany and a former Goldman Sachs banking executive, is waiting for the outcome of a task force study on the cap's effectiveness.

"The data is overwhelming," Michael Darcy, the executive director of the New Jersey League of Municipalities, said. "Sometimes things become so obvious that you don't need a report. We know this thing is having a huge positive impact."

Christie, speaking at a public event about opioid addiction, used stronger words.

"He's a coward, an absolute coward and he's a political charlatan. He's trying to be everything to everybody," Christie said.

"Legislative leaders have said to me they're looking for a signal from Ambassador Murphy, who is the leader of their party right now," he said. "And he's been unwilling to take a position on this -- that's not leadership."

Property taxes in New Jersey went up an average of 2.37 percent since 2010, according to Darcy. That's in thanks part to a 2 percent cap on property tax levies and the interest arbitration cap.

Without the interest arbitration, New Jerseyans can expect to see their property taxes "go back to the 5 percent, 6 percent or 7 percent" annual increase same towns witnessed prior to 2010, Darcy said.

"It's a proven tested solution to the property tax problem," he said.

Murphy's opponent, GOP nominee Lt. Gov. Kim Guadagno, has also criticized Murphy for not embracing the cap.

But the Murphy campaign brushed Christie's criticisms aside.

"Phil has already said he is open to all solutions that would help make New Jersey more affordable. And Governor Christie has proven time and time again that he's more interested in bullying and name calling than leading," Murphy spokesman Daniel Bryan said.

"After eight years of rising property taxes and costs of living, and an economy stuck in the swamp, Chris Christie and Kim Guadagno have no credibility with the people of New Jersey," he said.

The governor, meanwhile, blasted Murphy for not giving his party "direction" or telling voters what they should know about him before they head to the polls.

"They're waiting," Christie said.

The Police and Fire Public Interest Arbitration Impact Task Force's report is due by Dec. 31. Voters head to the polls to pick Christie's successor on Nov. 7.

The New Jersey League of Municipalities, along with the state's Association of Counties and Conference of Mayors, are holding a news conference Friday to pressure lawmakers to not let the measure sunset. The groups are made up of Democratic and Republican officials.

"Our task is going to be that the legislature takes care of this before the end of the year," Darcy said. "Get it done so there's no gap."

It's up to the New Jersey Legislature to vote on whether to renew the cap before the governor can sign any bill.

State Senate President Stephen Sweeney, D-Gloucester, told NJ Advance Media that legislative leaders are waiting for the report to come out before making a move.

"And then we'll sit down with the new administration, whoever that is, to make a decision," Sweeney, D-Gloucester, said.

NJ Advance Media staff writer Brent Johnson contributed to this report.

Matt Arco may be reached at marco@njadvancemedia.com. Follow him on Twitter @MatthewArco or Facebook.