Former Secretary of State Hillary Clinton has been "cheating the U.S. government for years," according to Republican presidential candidate Donald Trump.

The outspoken billionaire upped his criticism of Clinton Thursday, describing the Democratic front-runner as belonging to the "weak, pathetic, sad people [in Washington] that don't have a clue, who don't do anything."

"Here's a woman cheating the U.S. government for years with her emails," Trump said. "I mean, they gave [Gen. David] Petraeus a criminal record and they destroyed about five other people for doing one-fifth of what she did."

Petraeus, the former director of the Central Intelligence Agency, plead guilty to a misdemeanor charge in March for mishandling classified information during his tenure at the CIA. He was later sentenced to two years probation and forced to pay a six-figure fine.

"I look forward to running against [Clinton] because frankly, that is going to be such a big issue," Trump said, referring to her the scandal surrounding her private email server.

"I think the Democrats are going to let her get away with it because they have a corrupt system," he added.

The real estate mogul also said his wife, Melania, and daughter, Ivanka, will appear more frequently on the campaign trail in coming weeks. Clinton has previously criticized the leading GOP candidate for his remarks about women and women's health.

"It's going to be great," Trump said. "They care so much, so strongly about women's health issues."