Speaking this morning on the Today programme on Radio Four, Christine Pratt said although two of the calls to the helpline had come from the deputy prime minister's office, none had accused the prime minister himself of bullying.
But Cary Cooper, who is patron of the National Bullying Helpline, stood down from his role, saying Pratt had breached confidentiality in talking to the press.
Pratt claimed: "I sent an email to my local radio station saying that I had seen Lord Mandelson saying there was no bullying going on and that, as far as I was concerned, this was not the way for an employer to respond."
Responding to the allegation the prime minister had bullied staff, she said: "Absolutely not, and nor have we said that Gordon Brown is a bully. Our concern here is the public statement from No 10 of denial ... we would just want Gordon Brown and No 10 to lead by example.
"We would have hoped that Gordon Brown would have said that he was looking into this, that due process was being followed, and that he takes these issues seriously."
