As the Democrats ramp up their fight against the Republicans ahead of November’s presidential election, Clinton told a conference in New York that she is keen for countries around the world to “collect taxes in an equitable manner, especially from the elites”.
Clinton, who is campaigning for Barack Obama’s reelection, added that leaders need to “tell powerful people things they don't want to hear” over their contributions to state spending.
Republican candidate Mitt Romney, who has proposed cutting income taxes, has come under fire for his own contributions.
He said that he thinks it is fair that he pays a lower tax rate on his investment income of $20m last year than someone who made $50,000 annually.
“Yeah,” Romney said in an interview aired on Sunday on CBS, when he was asked if he thought his relatively low rate was fair.
Romney released his 2011 return on Friday, which showed he paid an effective tax rate of 14.1 percent. Romney pays a lower tax rate because his earnings come from investment income. Earnings from wages can be taxed at a rate of up to 35 percent.
Romney has steadfastly refused to release more than two years of his tax returns, breaking a longstanding presidential campaign tradition.
Democrats contend Romney is hiding something, arguing that the American people have the right to the information so they can make their own judgments about the finances of a potential future president.
Romney has said releasing the returns would just give his rivals' "hundreds of thousands of more pages to pick through, distort and lie about.”
But Barack Obama is facing his own set of problems. The President is due to speak at the UN General Assembly today, amid close scrutiny of his foreign policy.
Relations with Israel, Afghanistan and Iraq have become sore spots on the campaign trail.
Speaking at the Clinton Global Initiative last night, Obama’s ally also urged those taking part in protests across the Middle East to eschew violence.