A lawyer and businesswoman, she ended up chief executive of the Australian Olympic Committee. It was rumoured that supremo John Coates was grooming her to take over from him as president.

Then suddenly, in October last year, following her 10th Olympic campaign in Rio de Janeiro, de Jong tendered her resignation.

She had no other job to go to. She said at the time she wanted to explore a global role closer to her husband's European family, and to spend more time with her young family.

Those things were true, de Jong has now told Fairfax Media. But the rest of the story was darker: it was about a powerful man who would not cede control, and a culture at the top level of the organisation he ran which tolerated bouts of serious bullying.

For 27 years, John Coates has run the Australian Olympic movement, a job which now earns him $760,000 a year. Now, for the first time, he is being challenged. A younger woman, former Hockeyroo Danni Roche, is campaigning to supplant him, take a huge pay cut and shake up Australia's Olympic culture.

Following the recent revelation that Coates told rival sports administrator John Wylie, "I don't shake hands with liars ... I don't shake hands with c---s," the culture of the organisation the Olympic chief presides over, and persistent allegations of bullying within it, have become a key issue in a campaign that has split Australian sport.

At the heart of the bullying claims is Mike Tancred, the AOC's powerful, aggressive, media director and John Coates's right hand man. Tancred is described by multiple sources as a "protected species" as long as Coates remains AOC president.

Fairfax Media can reveal that Tancred has been the target of a number of complaints, formal and informal, from staff over many years. Each time he has survived, while the alleged victims have felt no option but to resign.

And it was Tancred who delivered the final indignity to his one-time boss, de Jong.

In December, well after she had tendered her resignation and as her leaving party was being prepared in AOC's Sydney headquarters, de Jong was trying to save her reputation from internal attack.

Another AOC executive had accused her of leaking board discussions to the press. She vehemently denied it, complained, and demanded the person withdraw the allegation. De Jong says that minutes after she sent her confidential complaint to Coates, her phone rang. It was Tancred.

"He said, 'Fiona, withdraw the complaint or I will bury you'."

Then, she claims, Tancred issued a highly detailed and personal threat. De Jong does not want to spell it out, except to say he was "abusive and threatening to me and would have affected my family life".

"The nature of his conduct could best be characterised as blackmail and intimidation," she says now.

"Over the course of my career I've been exposed to plenty of heated discussions, and poor choice of words or bad language in the workplace, but this went way beyond that.

"It's one thing to take me on, but quite another to involve my family."

Later that evening, de Jong formally complained to Coates about Tancred, copying in the chief financial officer, who was as close to a human resources manager as the AOC had at the time. Four months later, she has heard nothing. De Jong believes the organisation is on a "go slow," waiting until after the May 6 election for the AOC presidency to address her complaint.

"There's no reason for such a delay," she says. "It's deeply disappointing when you stand for a matter of integrity and it's swept under the carpet by the very people that are there to uphold it."

De Jong says the leadership of any organisation has responsibility to provide a safe workplace for employees. Her motivation is "in the interests of the staff and members of future Olympic teams," she says.

Tancred declined to comment on this, or any other bullying complaint. When Fairfax Media asked him last month about allegations against him, Tancred said they were "isolated issues" and all were "years ago".

Through lawyers, Coates did not respond to a question about whether the AOC's culture tolerated bullying. Of de Jong's complaint, he said it was "unfair and prejudicial" to those involved for its details or the outcome to be the subject of "speculation".

It could not be resolved now, he said, because "the AOC election will affect the membership of the AOC Executive".

History suggests that, if Coates wins the election, Tancred will continue in his $320,000-per-year job. Over the many years that allegations have been made against Tancred, Coates has sometimes prescribed anger management courses, sometimes changed Tancred's line of responsibility so he reported direct to him.

Meanwhile, "everyone who has ever complained has been the one who left," de Jong says.

It was 2004 when Ryan Wells, a British citizen on a working visa, says he was threatened as he sat at his desk at the AOC office in Sydney.

"Mike Tancred came in," Wells recalls. "He stood about 60cm from me, stood over me and threatened me: 'I will kill you'."

Wells does not remember exactly what the disagreement was about, but, "I remember not having a chance to have a discussion - it came out of the blue, he was aggressive, menacing."

"I was quite shaken about it. I felt very sick. It was a horrible confrontation."

Wells complained verbally to senior AOC secretary general Bob Elphinston and director of sport Craig Phillips but nothing really changed, Wells says.

He later received a negative assessment from Tancred in a report on the 2004 Olympics and, six months later, was made redundant.

"For me it had very large consequences: I had to leave Australia and the job I love. That really makes me angry today, the injustice of that," Wells says.

"There's such a double standard here. If this was an athlete, they'd get kicked off the team for getting back to the village at 6 o'clock in the morning, but you can have 12 years of this sort of thing and nothing. It just beggars belief."

A number of cases followed. In 2008 a young woman complained about Tancred yelling, swearing, and questioning her commitment. She left soon afterwards. In 2013, a second young woman lodged a formal complaint about Tancred's alleged unpredictability and frequent furious outbursts.

Employees from that time recall that, ironically, the complaint arose after Coates put staff through a bullying awareness course that had been inspired by complaints against the then chief executive of retailer David Jones, where Coates was deputy chairman.

That time, sources say, a finding akin to inappropriate conduct was made against Tancred - something short of bullying. He was supposed again to change his behaviour, but former colleagues say he did not. The young woman left her job a year later, still unhappy.

A similar thing happened in 2015 with a third young woman, who documented a series of blow-ups with Tancred. De Jong says the woman raised these issues informally, considering it futile to formalise the complaint.

Soon afterwards, sources say Coates stepped in and heavily criticised the woman in communications with senior management over an apparently unrelated issue. Coates ordered her to apologise for "wasting his time".

Shortly afterwards, she quit the AOC.

Through lawyers, Coates said he "strenuously denies" that he took any action against the young female worker "for having made an informal complaint against Mike Tancred" nor that he took "any other adverse action against her as a result".

The following year, Tancred received a $32,000 pay rise. His total package is now $330,000, the highest in the organisation below Coates himself and the chief executive.

"Tancred's and Coates are incredibly loyal to each other," says one former staff member.

"I can't imagine any other workplace where an employee has multiple formal and informal complaints raised against him, and he continues to work there."

Coates said Tancred's remuneration was determined by the AOC Remuneration and Nominations Committee of which Coates was not a member.

On May 6, 40 sporting organisations and the members of the Australian Olympic Committee board will gather at the Museum of Contemporary Art to decide whether Coates remains at the helm, or is replaced by former hockey champion Danni Roche.

Fiona de Jong did not want to be part of any campaign, but she feels, for the sake of the staff, she cannot remain silent.

"My motivation is sincere in my concerns for the AOC staff that remain," she says.

"Sadly, this has become an organisation that falls short when it comes to upholding the very standards we ask of our Olympic athletes."