New voting laws in 23 of the 50 states could keep more than 10 million Hispanic U.S. citizens from registering and voting, a new study said on Sunday, a number so large it could affect the outcome of the November 6 election.

The Latino community accounts for more than 10 percent of eligible voters nationally. But the share in some states is high enough that keeping Hispanic voters away from the polls could shift some hard-fought states from support for Democratic President Barack Obama and help his Republican rival, Mitt Romney.

The new laws include purges of people suspected of not being citizens in 16 states that unfairly target Latinos, the civil rights group Advancement Project said in the study to be formally released on Monday.

Laws in effect in one state and pending in two others require proof of citizenship for voter registration. That imposes onerous and sometimes expensive documentation requirements on voters, especially targeting naturalized American citizens, many of whom are Latino, the liberal group said.

Nine states have passed restrictive photo identification laws that impose costs in time and money for millions of Latinos who are citizens but do not yet have the required identification, it said.

Republican-led state legislatures have passed most of the new laws since the party won sweeping victories in state and local elections in 2010. They say the laws are meant to prevent voter fraud; critics say they are designed to reduce turnout among groups that typically back Democrats.

Decades of study have found virtually no use of false identification in U.S. elections or voting by non-citizens. Activists say the bigger problem in the United States, where most elections see turnout of well under 60 percent, is that eligible Americans do not bother to vote.

Nationwide, polls show Obama leading Romney among Hispanic voters by 70 percent to 30 percent or more, and winning that voting bloc by a large margin is seen as an important key to Obama winning re-election.

The Hispanic vote could be crucial in some of the battleground states where the election is especially close, such as Nevada, Colorado and Florida.

For example, in Florida, 27 percent of eligible voters are Hispanic. With polls showing Obama's re-election race against Romney very tight in the state, a smaller turnout by Hispanic groups that favor Obama could tilt the vote toward the Republican.