DES MOINES — Iowa Attorney General Tom Miller announced Tuesday that he’ll not defend the state against a lawsuit from labor over Iowa’s new collective bargaining law.Miller, a Democrat last elected in 2014, said he’ll ask the Iowa Executive Council to seek outside legal help in defending the state against a challenge to the constitutionality of the law, which last week was passed by the Republican-controlled Legislature and signed into law by GOP Gov. Terry Branstad.

The state’s largest public-sector union, the American Federation of State, County and Municipal Employees Iowa Council 61, filed the lawsuit Monday in Polk County District Court taking on House File 291.

“As the new collective bargaining law has the potential to existentially threaten the viability of public sector unions — many of the very same organizations that have supported me in the past — I am recommending that the Executive Council seek outside legal representation to defend this lawsuit in order to avoid any questions about a potential conflict,” Miller said in a statement.

“While the extraordinarily professional and skilled attorneys in my office have vigorously defended Gov. Branstad and the Legislature in past lawsuits involving AFSCME, I think it’s most prudent in this highly charged legal dispute to avoid any appearance of politics clouding our office’s legal representation and judgment.”

The Iowa Executive Council, made up of the governor, secretary of state, state treasurer, secretary of agriculture and state auditor, must approve the appointment of outside counsel to represent the state — at an additional cost to be determined.

Branstad spokesman Ben Hammes said he didn’t have anything to add beyond Miller’s statement.

“He summed it up when he said that AFSCME had supported him in the past and he wants to avoid any questions about a potential conflict,” Hammes said in a statement.

The collective bargaining overhaul, which went from being unveiled to being signed into law in just a 10-day span, establishes two categories of public employees, some with more bargaining rights than others.

Unions not considered for public safety workers — which would be for groups including teachers, nurses, secretaries and others in state or local governments — are limited under the law in negotiating for wages only. Other topics such as benefits are not allowed at the bargaining sessions unless both sides agree.