Michael Marks from London's Metropolitan Mortgages claimed Lewis was such a good worker that he kept a job waiting for her even after she won X Factor in 2006.
He told The Sun: "Had she not had this success there would have been a job for as long as she wanted it. She was very bright, very intelligent and did her job exceptionally well.
"I even offered her an opportunity to train as a mortgage broker. But I've come to terms with the fact she's not coming back."
Lewis became the first British female solo star to top the US album chart with a debut LP earlier this week. She sold over 205,000 copies of her Spirit record to top the Billboard 200.