COLUMBUS, Ohio (AP) — A lawsuit was filed Thursday challenging Ohio’s newly drawn state legislative districts as giving an extreme and unfair advantage to the Republican Party.

The American Civil Liberties Union, its Ohio arm and a law firm filed the litigation on behalf of the League of Women Voters of Ohio, the Ohio Chapter of the A. Philip Randolph Institute and several individuals.

The litigation is believed to be the first such legal action in the nation against district maps prompted by the 2020 census.

It targets a map the powerful new Ohio Redistricting Commission passed in a 5-2 vote along party lines last week. The panel failed to reach the bipartisan consensus necessary to pass a 10-year map of state House and Senate districts and so was forced to create a four-year map.

Republican Senate President Matt Huffman, who took a leading role in crafting the map, said it would likely yield 62 Republican seats in the 99-seat Ohio House and 23 Republican seats in the 33-seat Ohio Senate.

Freda Levenson, legal director of the ACLU of Ohio, called that an “extreme partisan gerrymander” that flagrantly violates the redistricting rules laid out in the Ohio Constitution, after approval by a strong majority of Ohio voters.

“The blatant defiance of the reforms that were overwhelmingly passed by Ohio voters just six years ago is not only a violation of law, but is also a slap in the face to the people of this state,” Levenson said in a statement. “We are going to this state’s highest court to ensure that Ohio voters are able to have a voice in their government.”

Under Ohio’s new redistricting system, the Ohio Supreme Court has original and exclusive jurisdiction over legal disputes over the map.

Huffman pushed back against accusations of gerrymandering in a Friday guest column in The Columbus Dispatch as based on “a false narrative.”

He said the map is “both constitutional and compliant” with the directives voters approved, and that it keeps districts compact and communities together.

“Make no mistake, special interest groups tried very hard to undermine the process by pressuring members to accept so-called ‘representational fairness,’” he wrote. “This is simply the basic definition of gerrymandering, as these groups insist on telling Ohio voters what is fair.”