Speaking at Reverend Al Sharpton’s National Action Network conference, Obama denounced Republican-led changes to voter ID laws. AFP

President Barack Obama has said that the Republican party is threatening voters' rights more than at any other time since the passage of the Voting Rights Act in 1965.

In his second speech on race issues in two days, Obama told Reverend Al Sharpton's National Action Network conference in New York: "The stark and simple truth is this: the right to vote is threatened today in a way that it has not been since the Voting Rights Act became law nearly five decades ago."

Obama condemned the recent rise in Republican-led changes to voting ID laws, which disproportionately affect ethnic minorities, students and the elderly.

"Let's be clear - the real voter fraud is people who try to deny our rights by making bogus arguments about voter fraud," Obama said.

"What kind of political platform is that? Why would you make that a part of your agenda, preventing people from voting?"

In June last year, the US Supreme Court struck down part of the Voting Rights Act, which was passed in 1965 to protect the democratic rights of African Americans and other minorities.

America did not stand up, did not march and did not sacrifice to gain the right to vote only to see it denied to their kids and their grandchildren
President Barack Obama

The portion struck down required a number of southern US states with a history of racial discrimination to obtain permission from the federal government before making any changes to voting laws.

The court's majority 5-4 decision said: "Nearly 50 years later, things have changed dramatically. Largely because of the Voting Rights Act, voter turnout and registration rates in covered jurisdictions now approach parity.

"Blatantly discriminatory evasions of federal decrees are rare and minority candidates hold office at unprecedented levels."

In 2013, seven states passed voter restriction measures, including identification requirements and a reduction in early voting.

On Thursday, Obama spoke at the Lyndon B Johnson presidential library in Austin, Texas, to mark the 50<sup>th anniversary of the passage of the Civil Rights Act.

"America did not stand up and did not march and did not sacrifice to gain the right to vote for themselves and for others only to see it denied to their kids and their grandchildren," he said.

"We've got to pay attention to this. Race still colours our political debates."