The allegations follow other claims of bullying against demoted Labour MP Meka Whaitiri, Botany MP Jami-Lee Ross, and outgoing Retirement Commissioner Diane Maxwell, who all dispute the claims - or, in Whaitiri's case, aspects of the claims - against them.
The Weekend Herald has obtained documents which show that during its investigations in August this year, Parliamentary Service heard allegations that Barry:
• swore and yelled at staff;
• called an employee "stupid";
• used derogatory terms about other elected officials, which made staff uncomfortable;
• referred to people with mental health issues using offensive terms like "nutter";
• discussed her employees' sexuality in the workplace;
• expected staff would do work for the National Party during office hours, which they felt unable to refuse while knowing it was wrong, because they were scared.
One staffer told investigators he believed there was a huge power imbalance and that Barry was "terrifying" and could "destroy my career".
When questioned by Parliamentary Service in August, Barry denied all of the allegations.
"In particular, she disputes the claims regarding her attitude and comments attributed regarding people with mental health issues," the investigation notes from her interview read.
"[She says] she does not use profanities and doesn't swear or behave inappropriately... MB absolutely refutes that she expects staff to complete party work during work time."
However, the Weekend Herald has heard recordings which appear to show Barry swearing in a work context, and others where she appears to call a local board member "barking", one a "waste of space", and another "a duplicitous piece of shite".
It has also seen messages from Barry - who rarely used email but instead spoke into the voice-to-text function on her phone - appearing to request political work be completed during office hours.
Examples included writing her column "Maggie's Messenger", where she encouraged people to vote for Northcote MP Dan Bidois, and completing a "Super Blues" brochure for an over-60s National Party conference.
A former staffer who came forward to the Weekend Herald told Parliamentary Service that, during some weeks, up to half his work was party work. Parliamentary rules strictly stipulate party work is not part of support staff's job.
According to her interview with investigators, Barry knew it was against the rules.
But in a different recording obtained by the Weekend Herald, Barry said the opposite to the staffer the day he was due to give evidence for his co-worker's personal grievance case.
In it she said writing brochures on office time was "legitimate", while acknowledging the investigators would not be impressed if they found out.
"It's how the world goes around," she said. "You know the lay of the land."
When questioned by the Weekend Herald yesterday, Barry said Parliamentary Service had looked into allegations from former staff.
"The allegations were vigorously denied and disputed and were thoroughly investigated by Parliamentary Service. There was no finding that bullying or harassment had occurred.
"The issues have all been resolved professionally and by mutual agreement. I have wished the employees concerned well and so I am surprised to see they are being repeated in a partial, selective and incomplete way."
She said she had "constructive and positive employee relationships", and might refer the recordings of her to police.
"I have never given consent to such recordings being made or released and I do not waive my rights to refer the matter to the police against those responsible for recording or publishing, if indeed a secret recording has taken place."
The allegations come as an independent review into bullying and harassment at Parliament was launched by Speaker Trevor Mallard this week.
National is also conducting an internal cultural review to ensure its staff feel safe, after accusations from several women that Ross harassed them.
At the time, leader Simon Bridges said he didn't believe there was an environment of abuse and power within the party. Barry also spoke out, saying bullying behaviour had "no place" in National.
The former staffer who spoke to the Weekend Herald said hearing that had made him feel sick.
"When you're the subject of bullying investigations it takes gall to claim that Jami-Lee Ross was a one-off, that there are no other bullies that the party is aware of," he said.
But the staffer said the final straw for going public was when he saw his former job advertised and feeling "awful" that the next person would go through the same experiences he had.
"I just couldn't take it. Parliamentary Service as an employer has an obligation to ensure its staff are safe. They can't guarantee that if they recruit someone to work for Maggie," he claimed.
He said Parliamentary Service clearly knew about Barry's behaviour - his manager from the service had even warned him during his induction Barry could be a difficult boss.
When he later complained to the manager that he was having trouble, he says he was told to document any inappropriate behaviour - which is why he had the recordings.
He believed the National Party must also know about Barry, because the whip's office had told him she could be "tough" with staff; the party lawyer was involved in the grievance case; he had emailed party chief of staff Jamie Gray with concerns after leaving; and had spoken to Barbara Kuriger, the whip, as part of the culture inquiry.
"I was pretty dissatisfied with her response. She said something like 'we just need to be nicer to each other'," he said.
A spokesman for National said it was not appropriate to comment on individual employment matters, and noted the party's cultural review to ensure a safe workplace.
"The National Party works hard to ensure a positive workplace," the spokesman said.
The former staffer never went back to work after giving evidence in the first investigation - because he believed Barry would see his evidence and no longer trust him - instead invoking a relationship "breakdown" clause which prompted the second investigation, and his exit.
He said he was contacted after the bullying inquiry was announced this week, and would give evidence.
The former staffer supportive of Barry, who did not want her name published, said Barry could be "firm", but had never seen anything resembling bullying from Barry - though she added that everyone had different definitions.
"On different days, people have different sensitivities, and people have different lines of what they can and can't tolerate."
She was surprised when the personal grievance case surfaced and the other former staffer stopped coming to work.
"It came as a huge shock to me that that particular person didn't step into the office again. I was blindsided. I was told not to contact him by Parliamentary Service. I had no idea."
She also said new staff members sometimes mistook parliamentary work for party work, and it often took time to realise what material, for example, should and should not carry a National Party logo.
She said she sometimes did party work when she worked for Barry, but did so on a volunteer basis from home and using her own email address.
The Weekend Herald has been unable to confirm the result of the first investigation into the personal grievance case.
Barry said she could not respond to individual employment matters because of the Privacy Act and employment law.
Parliamentary Service, which is not subject to the Official Information Act, also said it could not comment on individual cases.
A spokesperson said Parliamentary Service might investigate claims parliamentary staff were doing party work.
"Employees who take part in any political activity, other than activities that are a function of their role, are required to ensure that Parliamentary Service resources are not used and that the political activities do not bring them into conflict with their primary duties as an employee of Parliamentary Service."
Barry said she welcomed the review into bullying at Parliament, which will be led by Debbie Francis.
Francis has said she may recommend bringing Parliamentary Service under the Official Information Act, which could improve behaviour.
Speaking about the Francis review earlier this week, Act leader David Seymour said MPs, and not Parliamentary Service, should be the boss of their staff, and the current arrangement means MPs can treat their staff with impunity.