HOUSTON, United States

The California Republican Party filed a lawsuit Wednesday to block new congressional maps approved by voters in the western US state the previous night, according to media reports.

The lawsuit, brought forward by State Assemblyman David Tangipa and 18 co-plaintiffs, alleges that Proposition 50 "unconstitutionally gerrymanders districts in violation of the 14th and 15th Amendments" of the US Constitution.

The premise of the suit argues that the maps are unconstitutional because they improperly use voters' race as a factor in drawing districts.

The approved ballot measure, championed by California Gov. Gavin Newsom, created a new congressional map to give Democrats five more of the state's 52 congressional seats.

Prop 50 was brought to the voters in response to lawmakers in the state of Texas approving new congressional maps that created the potential for five additional Republican House seats. That measure was signed by Gov. Greg Abbot without voter approval, with a Republican-majority Texas legislature passing the bill.

Texas was one of several Republican-led states that US President Donald Trump pushed to change their congressional maps ahead of next year's midterm elections.

Ohio, Missouri and North Carolina have already redrawn their maps this year, which will boost the number of Republican House seats.

Republicans have a razor-thin three-seat majority in the US House of Representatives, and the goal of creating new voter maps was supported by Trump to retain Republican control in Congress.

The California lawsuit is being represented by Dhillon Law Group, founded by Harmeet Dhillon, who works for the US Justice Department.

It is not clear how successful the challenge will be, as California Republicans failed to prevent the Prop 50 ballot measure from making it to voters.​​​​​​​

Democratic leaders have expressed confidence that the new House maps would withstand legal challenges.