CONCORD — The state Department of Justice has lined up six nationally known law firms to represent New Hampshire in its landmark lawsuit against major chemical companies over contamination from chemicals used in products with trade names like Teflon and Scotchgard.

The Executive Council and Legislative Fiscal Committee have both approved a June 11 agreement that guarantees the law firms 20 percent of any settlement, after expenses.

Gov. Chris Sununu and Attorney General Gordon MacDonald in May announced the lawsuit was filed in Hillsborough County Superior Court against 3M, DuPont and the Chemours Company, all of which manufacture and distribute chemicals known as PFAS (polyfluroalkyl substances).

A separate lawsuit was filed against the companies responsible for firefighting foam containing some of the same chemicals, including Chemguard, Tyco Fire Products, Buckeye Fire Equipment, Kidde-Fenwal and National Foam.

DuPont, 3M and Chemours, a spin-off from DuPont, are named in both suits. The suits allege that despite their unique knowledge of the dangers of these chemicals, the companies continued to make and sell them without warning the public of their health risks.

The lawsuits seek damages for contamination of the state’s natural resources and will seek to recover costs related to the investigation, cleanup and other forms of response to contamination.

One of the six law firms retained by the state is SL Environmental Law Group of San Francisco, which specializes exclusively in environmental litigation.

That firm represented New Hampshire in 2013, when a Superior Court jury awarded the state $236 million in a lawsuit against ExxonMobil for groundwater contamination caused by the gasoline additive MTBE.

By the time appeals were exhausted, the principal and interest owed the state had grown to $300 million.

MacDonald said the award in the PFAS case could match or exceed the ExxonMobil verdict if the state prevails in court or reaches pre-trial settlements.

The other law firms retained are:

• Kelley Drye & Warren, a New York firm with more than 40 areas of specialization identified on its website, including environmental litigation;

• Taft Stettinius & Hollister, with offices in Chicago and eight other cities, also has multiple areas of expertise, including environmental litigation;

• Douglas & London, a New York law firm specializing in personal injury and class action lawsuits;

• Levin Papantonio, of Pensacola, Fla., which also has multiple lines of practice, including personal injury, class action and environmental; and,

• Kennedy & Madonna, a New York law firm co-founded by Robert F. Kennedy, Jr., that specializes in representing individuals, municipalities and states that have been impacted by pollution.

The six firms have formed a consortium to represent plaintiffs in PFAS or similar lawsuits. Officials from the Department of Justice interviewed lawyers representing two such groups before settling on one, according to Chris Aslin, senior assistant attorney general.

“We typically do not issue requests for proposals for legal counsel contracts,” he said.

In this case, Attorney General Gordon MacDonald consulted with Senior Assistant AG Alan Brooks, chief of the Environmental Bureau at the DOJ, as to which groups of lawyers should be considered.

“He identified those firms or groups of firms that have had experience with this issue, and we reached out to them,” said Aslin. “We had two of them in for interviews and presentations. We reviewed those presentations and their credentials and made a decision about what group of firms to hire.”

Brooks will serve as the main contact with the attorneys, with Aslin as his backup. The agreement with the attorneys was posted prior to consideration by both the Executive Council and Fiscal Committee.

“The process we followed after selection was very transparent, very public and very consistent with all of the laws,” said Associate Attorney General Dianne Martin.