The Obama administration on Monday blocked a new law in Texas that requires voters to show a photo ID, drawing fierce criticism from Republicans who say the move was aimed at boosting President Barack Obama’s re-election prospects.

The Justice Department said that the law disproportionately harms Hispanic voters.

“Even using the data most favorable to the state, Hispanics disproportionately lack either a driver’s license or a personal identification card,” Thomas Perez, head of the Justice Department’s civil rights division, wrote in a letter to Keith Ingram, director of elections for the Texas secretary of state.

The action follows a similar move in late December to block a voter ID law in South Carolina that federal officials said adversely affects black voters.

The challenges are part of an escalating national legal battle over voter ID laws that has become more intense because it is an election year. Eight states passed voter ID laws last year, and critics say the new statutes could hurt turnout among minority voters and others, many of whom helped elect Obama in 2008. But supporters of the measures — seven of which were signed by Republican governors and one by an independent — say they are needed to combat voter fraud.