WESTPORT — The Westport police union has voted down a pension plan and new contract with the town, the similar set of agreements the firefighters union and Representative Town Meeting approved a month ago.

“I certainly was surprised,” said Floyd Dugas, the town’s municipal labor and employment lawyer. In most cases, the police and fire unions agree on the same pension plans and contracts, said Dugas, a senior partner with Berchem Moses.

“Usually when you entered into a tentative agreement with somebody, it goes through and the people negotiating that have the pulse of the membership,” Dugas said.

He said the decision of Westport Police Local 2080 to vote down the set of agreements earlier this month was especially surprising, considering union and town negotiators had already come to a tentative agreement, something with which Ralph Chetcuti, the town’s director of personnel and human resources, agreed.

“Frankly, I was surprised, especially after the fire union approved it,” he said. “In a nutshell, the union rejected the last plan we put out where we lowered the contribution to the defined contribution to the pension plan from 10 percent to 9 percent” for employees hired prior to July 1, 2017.

Police union head Officer Scott Morrison did not respond to repeated calls for comment on why the union rejected the pension plan and contract.

Over the last several years, the town has dealt with a series of pension re-negotiations, including for the Public Works Department and town employees.

“The deal we offered and agreed to with the police is consistent with all of those,” Dugas said. “It’s somewhat surprising they wouldn’t agree to essentially similar terms, if not better, than those offered to and accepted by all those other employees.”

Because the police union rejected both contracts, the case will return to arbitration, probably sometime within the next several months, Chetcuti said.

“It’s suspect they’re reluctant to give anything up, but this is a new day and age. All you have to do is look at the state level to understand this is not the 1980s and 1990s anymore,” Dugas said, saying revenue sources at the state level have dried up, while the rate of retirement among baby boomers has resulted in medical costs rising at a higher rate than cities are able to raise taxes.

“We have to adjust benefits to the realities of today,” he said.