Montgomery County has hired about two dozen temporary employees to work at polling places and urge voters to approve a county law that places limits on collective bargaining for the police union.

The union, which is waging a vigorous campaign of its own, immediately struck back, issuing a statement Thursday that said the use of county resources for political purposes is “unfair,” “improper” and “unprecedented.”

County spokesman Patrick Lacefield, who said the county is spending about $5,000 on the hirings, defended the practice.

“We’re doing exactly what we’re entitled to do and what would be expected,” Lacefield said. “There is no obligation for the county to be silent in defense of county policy, which special interests spend money to misrepresent.”

The police labor law, approved by the county council last year, would remove a method of bargaining that the police union has had for three decades. The union successfully put the law to a referendum in August.

Since then, the county and police union have spent hundreds of thousands of dollars on the campaign. The county has distributed fliers, sent out e-mails and created a Web site in support of what’s known on the ballot as Question B. The police union has hired two outside consulting groups, created its own Web site and gone on television to urge residents to strike down the law.

Jared DeMarinis, director of candidacy and campaign finance at the state board of elections, said the hiring of campaign workers by a local government is highly unusual in the state.

The Maryland State Prosecutor opened — and then quickly closed — an investigation into whether county officials improperly used county resources during the referendum campaign. The prosecutor, Emmet C. Davitt, closed the investigation because he found that the county had acted in good faith.

But in a letter to state Attorney General Douglas F. Gansler, Davitt sought an opinion on how the government can use public resources during referendum campaigns, if it can at all.

Orly Lopez and Jennifer Lopez, two workers who are not related, were standing at the early voting site at the Bauer Drive Community Recreation Center in Rockville on Thursday. They said they found out about the job Wednesday and were being paid $12 an hour. Jennifer Lopez, 17, said she found out about the job from officials at Identity, an organization that helped troubled Latino teens in Montgomery County.

Orly Lopez, 18, said he’s been looking for a permanent job for a week. He’s taking classes at Montgomery College, and he wants to work in automobile mechanics or criminal justice. Though he was being paid by the county, Lopez said he voted to strike down the county law. “My dad’s in the union,” he said.

The issue of county resources being used in referenda campaigns has also come up in Prince George’s County, which has become ground zero in the fight over whether to expand gambling in the state and build a Las Vegas-style casino at National Harbor.

Council member Mel Franklin (D-Upper Marlboro), a onetime gaming foe, recently spoke in the county government building on behalf of expanding gaming in Maryland alongside several elected officials, including council members Will Campos (D-Hyattsville) and Derrick Leon Davis (D-Mitchellville) and County Executive Rushern L. Baker III (D).

Gaming opponents called foul and questioned the use of government property, and Baker’s frequent countywide e-mails from his office, to advocate for Question 7, as the gambling measure is known on the ballot.

Josh Hamlin, an attorney for Prince George’s County, said he had researched the matter thoroughly and countered that officials were well within their rights to advocate when the county’s interests are at stake.

This week, the pro-gaming side zeroed in on the mayor of tiny Forest Heights, population 2,400, which sits in the shadow of National Harbor. Mayor Jacqueline Goodall has made no secret of the fact that she is on the payroll of the anti-gaming forces, as described in a recent Washington Post article.

After the story was published, Del. Mike McDermott, an Eastern Shore Republican who is backing gaming expansion, wrote to Davitt, the state prosecutor, to ask whether Goodall is abusing her office by being a paid employee of the anti-gaming forces. James I. Cabezas, the state prosecutor’s chief investigator, said the office would not comment.

“It is troubling to me,”McDermott said. “It should be troubling to everybody.”

Neither Goodall nor Forest Heights attorney Kevin Best were immediately available for comment.