Democratic presidential candidate Hillary Clinton. Jeff Swensen/Getty Images Democratic presidential nominee Hillary Clinton has been increasingly dogged by questions about the relationship she had with the Clinton Foundation while serving as secretary of state, adding a thorn in her side at a crucial point in the campaign season.

Donald Trump, her Republican opponent, and his surrogates have repeatedly accused Clinton of providing top foundation donors with favors. Trump has alleged that she ran a "pay-to-play" operation during her years as the department's head.

"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 Monday statement. "It is now clear that the Clinton Foundation is the most corrupt enterprise in political history."

The brash billionaire concluded his statement by calling for the Clinton Foundation to be "shut down immediately."

The Republican nominee's call for the Clintons to close their foundation came as Judicial Watch, a conservative watchdog organization, released a batch of new emails on Monday that it said proved that Clinton provided donors with special access.

In one of the emails, Douglas Band, an executive at the Clinton Foundation, appeared to bypass normal State Department channels to request a meeting for Crown Prince Salman of Bahrain.

"Good friend of ours," he wrote Huma Abedin, a top Clinton aide.

The meeting was later arranged.

Another email exchange showed Band seemingly attempting to assist Casey Wasserman, president of the Wasserman Foundation and a top Clinton Foundation donor, with getting a visa for a person having trouble because of a "criminal charge."

Abedin wrote to Band that getting involved in the matter "makes me nervous." Band then advised her not to.

Clinton has previously denied allegations that she provided special treatment to foundation donors.

"There is absolutely no connection between anything that I did as secretary of state and the Clinton Foundation," she said in July.

John Podesta, Clinton's campaign chairman, dismissed the allegations in a campaign statement on Monday afternoon and said that voters did not need to fear a conflict of interest if Clinton were to become president.

"The Foundation has already laid out the unprecedented steps the charity will take if Hillary Clinton becomes president," he said.

Podesta instead encouraged Trump to "come clean with voters about his complex network of for-profit businesses that are hundreds of millions of dollars in debt to big banks" and demanded he "release his tax returns."