US Republican presidential nominee Donald Trump slammed the charitable Clinton Foundation, calling it a "corrupt enterprise," and demanded Hillary Clinton shut it down.

"The Clintons have spent decades as insiders lining their own pockets and taking care of donors instead of the American people," Trump said in a statement.

"It is now clear that the Clinton Foundation is the most corrupt enterprise in political history," Trump said, blasting the charity, which has raised some $2 billion (1.8 billion euros) over the years.

The foundation, which was founded in 2001 by her husband, former US President Bill Clinton, has helped millions of people worldwide.

In an email to supporters, Bill Clinton defended the charitable foundation, saying it has "improved millions of lives around the world."

Trump said the foundation had received financial contributions from various countries "that discriminated against women and gays and everybody else."

He was apparently referring to some countries' checkered pasts and poor human rights record, including Saudi Arabia, which made sizable donations to the philanthropic organization while Hillary Clinton was secretary of state between 2009 and 2013.

"I mean, that money - it should be given back," Trump said. "They should not take that money."

Foundation is charity organization

Hillary Clinton's campaign manager, Robby Mook urged the public to remember the "important, lifesaving work" the foundation has done over the past 15 years.

"Over 10 million people around the world get important AIDS medication, lifesaving AIDS and HIV medication because of the foundation," Mook said, adding that "the foundation has reduced the cost of malaria drugs by 90 percent."

But there are questions about potential conflicts of interest while Clinton, currently the Democratic presidential nominee, worked as Obama's secretary of state.

A proverbial firewall was supposed to have ensured that the foundation's work remained completely separate from Hillary Clinton's role as America's top diplomat, but critics say the barrier wasn't foolproof.

In an attempt to quell the controversy Bill Clinton announced last week that the foundation would stop accepting foreign and corporate donations if his wife is elected president in November, and that he would step away from the foundation's board.

He added that additional measures would also be installed to ensure a complete division between the foundation and the White House under a Hillary Clinton presidency.

"Much of the foundation's international work, like that of most global NGOs, is funded in part by donor governments' bilateral aid programs," Bill Clinton said in a statement on Monday. "If Hillary is elected, we will transition those programs out of the foundation to other organizations committed to continuing their work."

bik/sms (AFP, AP)