The latest case of U.S. Secret Service agents blocking reporters from asking Democratic presidential candidate Hillary Clinton are "dangerous," and could lead to media being threatened for getting too close to the candidate, according to a long-time former agent.

Dan Bongino, who was on Clinton's security detail when she ran for the Senate in 2000, told Secrets, "This is dangerous. This is a dangerous development."

He explained: "It's dangerous because you have an arm of the federal government now de facto controlling access for a free press to a major presidential candidate. I mean, where does it end? What's next, do you start threatening people for asking questions?"

Bongino, author of the new book "The Fight, A Secret Service Agent's Inside Account of Security Failings and the Political Machine," added, "When you get the guys with guns involved, you start breaching a dangerous red line here. This is a staff function only."

Clinton's agents were criticized last year when they roped off reporters covering Clinton's participation in a parade.

This week, Fox News White House correspondent Ed Henry tweeted that agents were trying to block reporters from Clinton in Nevada. "Is that really their job?" he asked.

Bongino said that press handling is a staff job, but that over time as agents get friendly with staff, they take on some of their jobs.

"I think what's happening is kind of a form of 'security regulatory capture.' What I mean by that is that the guys now with the Clinton campaign are becoming really close with the staff because they've been there a while, I've seen it happen. And they're doing the staff's job with guns which is very dangerous. They should not be doing that, that's the staff's job," said Bongino, who has popular podcast on Conservative Review.

"My guess is that the tightness that's developing...between the staff and the Secret Service is leading to this whole, 'Hey Secret Service agent Joe, do you mind doing me a favor,'" he added.

The new book from Bongino, who was an agent during the Clinton, Bush and Obama administrations, is being released by St. Martin's Press on Monday.

Paul Bedard, the Washington Examiner's "Washington Secrets" columnist, can be contacted at