Stella English beat 15 other wannabe apprentices to win series six of the hit BBC1 show in 2010.
She was given a role in Lord Sugar's Viglen division, supplying IT equipment to academy schools, but she said that when the business mogul told her he would not be renewing her contract she was given no choice but to resign.
She is claiming constructive dismissal against Lord Sugar, who attended the hearing at East London Employment Tribunal Service today.
Ms English, of Whitstable, Kent, said she had no real role at Viglen and was not taken seriously by her colleagues, while she did not feel like Lord Sugar's "apprentice" as she said she only saw him five times during her 13-month employment.
Ms English, describing the first day of a four-month probationary period she and the other semi-finalist had to carry out before one of them was declared the winner, said: "No specific duties were allocated to me.
"I was provided with a desk and a phone but that was pretty much it."
Ms English fought back tears as she said she was given no guidance about what she was meant to be doing, and was "ostracised" by her colleagues who told her she had taken over another women's job which had a salary of £35,000.
Relegated to carrying out basic administrative tasks, Ms English said her employment was a "sham".
She added: "The career-enhancing opportunities that The Apprentice position had been sold as simply failed to materialise."
Ms English said that when she looked through the company's accounts she realised that although it had a £60 million turnover, it only made an £800,000 a year profit.
She said that when she then emailed her boss, Bordan Tkachuk, to ask if she could discuss this with him - and that she had noticed that projects worth £1.4 million had not been invoiced - he sent her a scathing reply, copying in everyone else in the office.
Ms English wept as she said he wrote to her: "I don't know what you're doing but this ain't how things work around here."
Dressed smartly in black trousers and a cream jacket and top, she told the tribunal that she emailed Lord Sugar to ask if she could discuss the matter with him but when he came to the Viglen office for a meeting with her, Mr Tkachuk was also present.
Ms English said she was upset when Lord Sugar asked his colleague what he thought of her and Mr Tkachuk replied: "Nice girl. Don't do a lot."
"They had never said this to me," she said.
Ms English said the job "became increasingly untenable to continue".
"As time progressed I continued to be marginalised," she added.
She said she phoned Lord Sugar in May 2011 and asked if she could meet him. "He made if abundantly clear that he didn't want to see me."
She said she told Lord Sugar: "I have tried so hard for so long and it's not working. I'm an overpaid lackey at Viglen. My pride would not allow me to continue doing it."
Ms English said Lord Sugar then offered her a role in another company which she started in June 2011.
"I decided to take up the position due to pressure from Lord Sugar who gave cause for concern that there might be adverse publicity due to me resigning," she said.
But she said she encountered similar problems in the second job.
On September 28, 2011, she said she was called for a meeting where she was told that Lord Sugar would not be renewing her contract.
She said Lord Sugar told her that he had given her the second role because he did not want to damage the integrity of The Apprentice or the BBC, or to arm his own public image.
Ms English said he added: "But the fact is that I don't give a s***."
Ms English, who left school with no qualifications but rose up to become the only female manager on the trading floor of a Japanese investment bank, taking home £82,500 a year, said she was shocked when Lord Sugar told her he would not be renewing her contract.
During questioning, she said she had actually begun to enjoy working at internet set-top box company YouView and was working really hard as she had heard that a business development management position was due to be coming up which she hoped to get.
Ms English, 34, said that Lord Sugar came into the office on September 28 for a separate meeting but came over and asked to speak with her when he saw her sitting at a different desk than normal as she was helping a colleague out with some other work.
"I assumed that he would be happy with this," she said. "I'd actively pursued different opportunities to do something useful."
She said of their subsequent meeting: "He said he basically wasn't going to be renewing my contract. That was the bombshell that I wasn't really expecting at all.
"Until that moment I had believed that I was doing a good job. I thought that he would be happy that I wasn't hassling him.
"I just really could not believe what he was saying. I was in absolute shock.
"I'd given two years of my life to be told by somebody that 'I don't give a s***'. All the effort that I'd put in - to be told this was so unnecessary."
The tribunal heard filming of the TV series took place from September to November 2009, with Ms English going away as a semi-finalist along with Chris Bates.
It was not televised until the following autumn, while her probationary period with Viglen took place from September 2010 to December of that year, before the final episode of the programme was filmed and she was crowned the winner.
During cross-examination from Seamus Sweeney, representing Lord Sugar, Ms English admitted she had been given a "talk of doom" by the series producers, as had all the other entrants.
In it, they were warned of the potential media publicity they would get from taking part and that it was not advisable for them to leave their current jobs entirely in case they did not win.
Ms English said her employers had given her a sabbatical while filming took place, but she quit the company to go and work at Viglen.
She said she did not remember being told that the winner might not work directly with Lord Sugar, adding that she understood they had in previous series.
"I didn't believe that they would pay me £100,000 a year to do anything less than £100,000 worth of work," she said.
"My reasons for going on to The Apprentice was to be an apprentice and to be mentored by Lord Sugar."
But she admitted: "I had my own interpretation of what the job was going to be. Nobody had ever said 'this is what it's going to be'."
Earlier, Lord Sugar sniggered as the tribunal was played clips of the TV show, in which he is described as "Britain's most belligerent boss".
Ms English said that on her first day at Viglen Mr Tkachuk looked at her with "contempt" and told her: "There is no job."
She said she often witnessed him displaying an "aggressive manner".
But she said she did not say anything to Lord Sugar as she "didn't want to be a troublemaker".
The tribunal was adjourned to 10am tomorrow when Ms English will continue to be cross examined.