Ms English, 34, who won Series 6 of the BBC1 show in 2010, is suing the millionaire business mogul, claiming constructive dismissal.
Reading out his own statement at the East London Employment Tribunal Service hearing today, Lord Sugar said he was surprised when she told him she was not enjoying the £100,000 role with him that she had won.
"I began to think that perhaps the reality of work rather than the glamour of showbusiness was beginning to bite with her," he said.
"Her time in the limelight was beginning to fade."
Lord Sugar went on: "In hindsight, I can now see that she was a very untrusting and suspicious person.
"It was clear to me now that she thought that everyone was out to trick her.
"She thought during the whole process that she was being lied to and that the other candidate has been chosen as the winner."
Lord Sugar said Ms English confronted him with the idea that semi-finalist Chris Bates had won the competition because she had not filmed a segment of the show showing her leaving his office in a chauffeur-driven car.
Lord Sugar added: "She always came across as quite reserved and detached and, some might argue, cold.
"At other times she would come to me with some very odd conspiracy theories."
He said she believed the PR agency he himself used had leaked information about her family to the press.
Lord Sugar said that Ms English attracted a lot of stories in the media as soon as the series was aired in the autumn of 2010, and before she had got anywhere near the final, including one that her fiance was connected to the Stephen Lawrence murder case.
Speaking of her suspicions that he had not really chosen her to be the winner, he said: "She assumed the whole thing was a charade and I had no interest in her."
Lord Sugar said it was not true that she told him she thought her role at his IT division Viglen was that of an "overpaid lackey," as she claims.
"That bit is a complete reconstruction or better described as a figment of her imagination," he said.
Lord Sugar also denied Ms English's claims that Viglen chief executive Bordan Tkachuk replied: "Nice girl. Don't do a lot" when he asked what he thought of her during a meeting between them.
"This is typical of her struggling to deal with the truth or facts," he said.
Lord Sugar said he thought Ms English had been doing well at Viglen although she had a lot still to learn.
He later gave her another role at internet set-top box company YouView after she resigned from Viglen in May 2011.
Earlier Ms English told the tribunal she had felt pressurised by Lord Sugar to take the second job.
She said he told him he needed a quick answer as the papers were going to print a story that she had quit the next day.
"I wasn't in a relaxed comfortable position," she said. "I would say that's a fairly pressurised situation.
"It was a completely new idea. Something that I hadn't had any forewarning about, therefore it was something I needed to consider."
Ms English, of Whitstable, Kent, said that Lord Sugar told her he would not be renewing her contract during an unscheduled meeting on September 28, 2011.
Ms English said: "He said to me 'look if you think Lord Sugar is s****ing himself and that's why you're here that's where you're mistaken - I don't give a s***.
"I've met my obligations to you.
"I did it for the BBC and the integrity of the show and a bit of my own PR and a bit of yours too. But the fact is that I don't give a s***."
Ms English said she could not believe that Lord Sugar was not taking her life and future seriously.
"At this point I thought we were living in the real world, not in a game show," she said.
Lord Sugar did not reach this stage of his statement today and will continue to read it out and give evidence tomorrow.
Ms English has told the tribunal that despite being paid £100,000 she had no clear role and only had basic administrative tasks to do at Viglen while she was "ostracised" by her colleagues who told her she had taken over another woman's job for which she was paid £35,000.
She told the hearing at East London Employment Tribunal Service that on her first day at Viglen its chief executive, Bordan Tkachuk, told her: "There is no job".
During cross-examination today she was asked by Seamus Sweeney, representing Lord Sugar, why she did not complain about how she was treated.
Dressed smartly in a black jacket and trousers and a coral shirt, she said: "I was in a trial period to win The Apprentice.
"What value is there in me going into a company I don't know - whether I knew (she was going to win) or not - and then go and complain about people who have been working there a long time.
"I didn't know at the time, within one month, how things were going to pan out."
Asked by Mr Sweeney why she did not drop out of the process if she was so unhappy, she said: "That's a very good question. It did cross my mind."
But she added: "I had still hoped that by not making complaints and not being difficult with these people that in time I could maybe win them over.
"I didn't feel to go through that process and then at the last minute to drop out was a real option.
"As I said it wouldn't have made any sense for me to do that."
Questioned about her relationship with Mr Tkachuk, she told the tribunal: "It was clear that he didn't think much of The Apprentice.
"He didn't have any real interest in me. He didn't really particularly want to speak to me.
"He did not acknowledge my existence at all and the fact of the matter is he didn't want me there."
The tribunal was adjourned.