Billionaire Republican presidential candidate Donald Trump has attacked the Indian- American aide of Hillary Clinton amid an email controversy surrounding the frontrunning Democrat.

Trump continued his attacks on Clinton at a Massachusetts fundraiser last night, saying the former Secretary of State has "some very big problems" with her email server.

The real estate mogul took things a step further by attacking longtime Clinton aide Huma Abedin and her husband, former Congressman Anthony Weiner calling him a "perv", ABC News reported.

"Who is Huma married to?" Trump asked. "One of the great sleazebags of our time. Anthony Weiner."

Weiner had resigned his Congressional seat in 2011, after it was discovered the Democrat took shirtless photos of himself and shared them with women online.

Clinton rep Nick Merrill released a statement, saying in part "Donald Trump has spent the summer saying offensive things about women, but there is no place for patently false, personal attacks towards a staff member. He should be ashamed of himself… it’s embarrassing to watch frankly".

Meanwhile, Clinton told reporters gathered at a press conference at the Democratic National Committee’s meeting in Minneapolis yesterday that the ongoing criticism and confusion over her use of a private email server at the State Department don’t frustrate her.

She is trying to do a better job of explaining the intricacies of the situation, Clinton added.

"I think that it is a little confusing, and I certainly understand why, for the press and for the public to try to make sense of this, like something wasn’t classified in 2009, 2010, but maybe now it should," she said of conflicting reports and interpretations on whether email sent through her private account contained classified government information.

"Maybe when we get all this behind us, people should say hey, ‘let’s take a deep breath here and try to figure out, is that the best process?’ But right now, it doesn’t frustrate me. It’s just the reality," she was quoted as saying by the Politico