Nicole, who has been dating the Formula 1 champ on and off for seven years, allegedly called time on their relationship because of Lewis' reluctance to marry and have children.
At the end of last year, former X Factor judge Nicole moved to the UK after landing a part in West End musical Cats, however the pair are said to have been arguing.
A source told The Sun: "She's finally had enough. Nicole knew Lewis had no plans to marry her, she's completely gutted and feels lost about her future."
Nicole's reps told Reveal that they do not comment on her personal life. We have also contacted Lewis' spokesperson.
Nicole, 36, and Lewis, 30, first began dating in 2007 and enjoyed a three-year romance before splitting at the beginning of 2010. The couple reconciled in 2011 and were on and off again until March last year.
In November, Lewis spoke about the difficulties of maintaining their relationship while also juggling equally hectic work schedules.
During the interview with This Morning, Lewis also remained coy when asked about having children with Nicole and explained that they are "both still young".
He said: "She's amazing with kids. I think we're both pretty good with kids but we don't have time for that at the moment.
"There are so many things we want to do, but the great thing is that we support each other with it. All in good time! She's still massively young and I'm still young!"
Opening up about their often long-distance love, he added: "With our careers people perhaps don't understand that she lives in LA, I live in Monaco and we're in and out all the time.
"Schedules are changing all the time. She's doing Cats now, which means she's here [in the UK] for the next two months and I go away and do my training.
"So during the year we're always apart, but people can see there's a lot of depth there - we've been together for almost seven years."
Former Pussycat Doll Nicole made her Cats debut in December and Lewis was quick to gush about how proud he was of her following her opening performance.
Alongside a picture of himself and Nicole, who was in full make-up and costume, he told his Instagram followers: "Went to see the Cats musical for the first time last night, and my lady @nicolescherzy blew me away!"
Neither Lewis or Nicole have mentioned the split claims on Twitter.
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