"They didn't ask me. I suppose I was fired!" Margaret told the magazine. "No, obviously they weren't going to want me to carry on doing interviews forever, and nor did I want to do them forever."
The Irish star, who was one of Lord Sugar's aides on the BBC show for four years, also spoke of how working with the Amstrad tycoon and fellow aide Nick Hewer on the show has helped her TV career.
"I'm pleased I did it," she said. "I went through a while of thinking that I wasn't happy, but now I am and it's opened doors for me."
The 62-year-old also plans to keep working on TV programmes with Countdown presenter Nick.
"We're hopefully doing something about railways," she said. "Nick and I do get on very well. We can be grumpy old people together."
Oxford graduate Margaret and Nick, who still acts as Lord Sugar's aide alongside Karren Brady, also recently presented a show called Too Many Immigrants? together.