Employees of Japanese firm Sanden testified that she was "aggressive" and "confrontational".
She was accused of making "disparaging" remarks about another worker's command of English which he found "extremely hurtful".
And in one case, she "thrust her face" close to a colleague and "screamed very loudly into his ear" leaving the man shocked and in pain.
Mrs Pratt yesterday refused to speak about the case.
She told the Mirror: "That's the subject of a tribunal, which is history - and it's one of the reasons I do what I do today.
"Also, it's not relevant to the issue we are raising with regard to the Prime Minister's office."
When pressed, she said: "Watch my lips, love you dearly - I'm not going to comment on it. It's raking up history."
Mrs Pratt faces a backlash about revealing details of calls to her helpline which are meant to be confidential.
Expert on workplace stress Professor Cary Cooper quit as patron of her charity saying: "I am resigning now. I think she breached confidentiality.
"One of the things that is really important for any helpline is to retain confidentiality."
Bullying UK director Liz Carnell said she was "horrified" and would complain to the Charity Commission.
She said: "Gordon Brown's office is small and the comments will almost certainly identify this person who turned to the helpline in despair.
"We suggest Mrs Pratt considers her position, given the damage she has caused to the antibullying sector."
Labour MP Anne Snelgrove said she had cut her ties with Mrs Pratt's Swindon-based charity after receiving complaints in 2008 that the helpline was used to find business for her husband's human resources consultancy.
A businessman told last night how he called the charity for help in 2007 and was asked by Mrs Pratt for a £300 deposit before she passed him on to an "associate". He was then hit with a £3,500 bill.
He said: "From what I could see they only made a few phone calls. I wouldn't advise anyone to go to them. They worked for me but it was not worth anywhere near £3,500."
A website that features alleged victims of NBH - under the banner "the last thing you need if you are being bullied" - questions the morality of a charity that asks desperate people for money.
Mrs Pratt has acknowledged the organisation offered to refer callers to her husband's consultancy but insisted that the arrangement was legal and had been properly approved.
Documents with the Charity Commission also showed last night that NBH is massively late in submitting its accounts. A spokesman said it had received several complaints about the organisation.
Source Daily Mail.