In the face ofmountingreports that Sen. Amy Klobuchar (D-Minn.) chronically mistreats her staff, the presidential hopeful has defended her office as a “tough” workplace that molds her employees for even greater challenges.

“Many of them have gone on to do incredible things,” she said in a recent interview with MSNBC’s Rachel Maddow. “I was teasing President Obama the other day: the White House hired over 20 of my staff members.”

But on a number of occasions, when her staffers have sought to land bigger and better jobs, Klobuchar has acted as their biggest obstacle. The senator is well known on Capitol Hill for calling prospective employers in an attempt to shut new job opportunities down — including at least one opportunity with the Obama administration.

Accounts of Klobuchar trying to thwart job-seekers come from half a dozen Capitol Hill staffers and former Klobuchar employees, all of whom requested anonymity.

In one instance, Klobuchar went so far as to confront a fellow Democrat in Congress who had offered a job to one of Klobuchar’s staffers to express her extreme displeasure and try to interfere with the hiring process, said a source with knowledge of their conversation. The member held their ground and the staffer ultimately made the jump.

On another occasion, Klobuchar blocked Obama’s Treasury Department from hiring one of her longtime aides. It’s common courtesy in Washington for the White House to ask senators of the same political party for their blessing before hiring their legislative staff. But instances of senators refusing are not common. The staffer in question was a finalist for a coveted job and “pissed” when Klobuchar refused to sign off, a source said.

Stories of Klobuchar mistreating her staff are challenging to the image she hopes will vault her into the White House: that of a personable, pragmatic Midwesterner who eschews drama and pettiness in favor of getting results.

But in Washington, Klobuchar has a well-established reputation for abusing her staff — and for undercutting their attempts to leave.

In an earlier report by Yahoo News, three former Klobuchar staffers and a Capitol Hill veteran described Klobuchar calling new employers to attempt to have them rescind job offers to her staff.

Do you have more information on what it’s like to work for Sen. Klobuchar — or other members of Congress? Get in touch: scoops@huffpost.com

Fear of Klobuchar’s interference is so prevalent that it has become the culture in her office to treat outside job offers like a state secret, former staffers told HuffPost. One former employee said that when she was looking for a new job, she warned potential employers that the senator might seek a way to sabotage her prospects.

Employers, of course, run reference checks on their prospective hires all the time. The phone calls and confrontations Klobuchar initiates are of a completely different nature, sources said. Her aim wasn’t to offer a candid evaluation of her staffers, negative or otherwise, they said, but to prevent highly desirable ones from taking their talents elsewhere.

As for her motivations, several former staffers noted Klobuchar’s conduct as a boss makes it difficult for her to replace outgoing staff. Her Senate office once suffered a long spell without an official chief of staff, HuffPost previously reported, and three different people turned down the offer to manage her nascent presidential campaign.

Former employees also told Yahoo News (a Verizon Media brand like HuffPost) that Klobuchar sometimes views it as a betrayal when her staffers quit.

After publication, Klobuchar’s presidential campaign provided the following statement: “This is completely false. The senator has never criticized her staff to prospective employers.”

A spokesman for the Congress member Klobuchar confronted would not comment for this story before publication. After publication, the spokesman said the story was not accurate. “This is just not true. There was no ‘confrontation’ in any way. She did not ‘express extreme displeasure’ in the conversation they had, nor did she ‘interfere in the hiring’ of an employee who had already been hired,” said the spokesman for the member.

On Friday, the New York Times reported that there were special constraints on employees who left after taking parental leave, at least on paper. Her office’s written policy effectively required those who took leave to remain in the office three times as many weeks as they had been gone, the Times said, or pay back the money they earned during their time off.

A Klobuchar spokeswoman told the Times that her office had never required anyone to repay their earnings and would change the language in its employee handbook.

As with an earlier report from Buzzfeed, the Times said Klobuchar has thrown objects such as binders and telephones at staffers. HuffPost and numerous outlets have reported that Klobuchar frequently berates staff and requires them to do chores in her house, such as laundry and dishes, and has generally created an anxiety-ridden workplace.

Klobuchar’s office consistently has one of the highest rates of staff turnover in the Senate.

Amanda Terkel contributed reporting.

This article has been updated with a statement from Klobuchar’s presidential campaign and includes two further statements from the Congress member’s office.

CORRECTION: Language has been updated to reflect that, in the case of the Congress member’s job offer, Klobuchar attempted to interfere with the hire. The article previously said she demanded the job be rescinded.